カルシウム Ca2+

WordNet

a white metallic element that burns with a brilliant light; the fifth most abundant element in the earths crust; an important component of most plants and animals (同)Ca, atomic number 20

PrepTutorEJDIC

『カルシウム』(金属元素;化学記号は『Ca』)
Calciumの化学記号

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/04/24 00:00:49」(JST)

wiki en

[Wiki en表示]

Calcium is a chemical element with symbol Ca and atomic number 20. Calcium is a soft gray alkaline earth metal, fifth-most-abundant element by mass in the Earth's crust. The ion Ca²⁺ is also the fifth-most-abundant dissolved ion in seawater by both molarity and mass, after sodium, chloride, magnesium, and sulfate.^[4] Free calcium metal is too reactive to occur in nature. Calcium is produced in supernova nucleosynthesis.

Calcium is essential for living organisms, in particular in cell physiology, where movement of the calcium ion into and out of the cytoplasm functions as a signal for many cellular processes. As a major material used in mineralization of bone, teeth and shells, calcium is the most abundant metal by mass in many animals.

1 Notable characteristics
- 1.1 H and K lines
2 Compounds
3 Isotopes
- 3.1 Isotope fractionation
4 Geochemical cycling
5 History
6 Occurrence
7 Applications
- 7.1 Calcium compounds
8 Nutrition
- 8.1 Dietary supplements
- 8.2 Bone health
- 8.3 Cardiovascular impact
- 8.4 Cancer
9 Cell signaling
10 Hazards and toxicity
11 See also
12 References
13 Further reading
14 External links

Notable characteristics

Flame test. Brick-red color originates from calcium.

In chemical terms, calcium is reactive and soft for a metal; though harder than lead, it can be cut with a knife with difficulty. It is a silvery metallic element that must be extracted by electrolysis from a fused salt like calcium chloride.^[5] Once produced, it rapidly forms a gray-white coating of calcium oxide and calcium nitride for reacting with the oxygen and nitrogen in the air when exposed to it. In bulk form (typically as chips or "turnings"), the metal is somewhat difficult to ignite, more so even than magnesium chips; but, when lit, the metal burns in air with a brilliant high-intensity orange-red light. Calcium metal reacts with water, generating hydrogen gas at a rate rapid enough to be noticeable, but not fast enough at room temperature to generate much heat, making it useful for generating hydrogen.^[6] In powdered form, however, the reaction with water is extremely rapid, as the increased surface area of the powder accelerates the reaction with the water. Part of the reason for the slowness of the calcium–water reaction is a result of the metal being partly protected by insoluble white calcium hydroxide; in water solutions of acids, where this salt is soluble, calcium reacts vigorously.^{[citation needed]}

With a density of 1.54 g/cm³,^[7] calcium is the lightest of the alkaline earth metals; magnesium (specific gravity 1.74) and beryllium (1.84) are denser though lighter in atomic mass. From strontium onward, the alkali earth metals become denser with increasing atomic mass.Calcium has two allotropes.^[8]

Calcium has a higher electrical resistivity than copper or aluminium, yet weight-for-weight, due to its much lower density, it is a better conductor than either. Its use as such in terrestrial applications is usually limited by its high reactivity with air; however, it has potential for use as wiring in off-world applications.^[9]

Calcium salts are colorless from any contribution of the calcium, and ionic solutions of calcium (Ca²⁺) are colorless as well. As with magnesium salts and other alkaline earth metal salts, calcium salts are often quite soluble in water. Notable exceptions include calcium hydroxide, calcium sulfate (unusual for sulfate salts), calcium carbonate and tricalcium phosphate. With the exception of calcium sulfate, even the insoluble calcium salts listed are in general more soluble than the transition metal counterparts. When in solution, the calcium ion varies remarkably to the human taste, being reported as mildly salty, sour, "mineral-like" or even "soothing." It is apparent that many animals can taste, or develop a taste, for calcium, and use this sense to detect the mineral in salt licks or other sources.^[10] In human nutrition, soluble calcium salts may be added to tart juices without much effect to the average palate.^{[citation needed]}

Calcium is the fifth-most-abundant element by mass in the human body, where it is an important cellular ionic messenger with many functions. Calcium also serves as a structural element in bone. It is the relatively high-atomic-number calcium in the skeleton that causes bone to be radio-opaque. Of the human body's solid components after drying and burning of organics (as for example, after cremation), about a third of the total "mineral" mass remaining is the approximately one kilogram of calcium that composes the average skeleton (the remainder being mostly phosphorus and oxygen).^{[citation needed]}

H and K lines

Visible spectra of many stars, including the Sun, exhibit strong emission lines of singly ionized calcium. Prominent among these are the H-line at 3968.5 Å and the K line at 3933.7 Å of singly ionized calcium, or Ca II. When observing the Sun, or stars with low temperatures, the prominence of the H and K lines in the visible spectra can be an indication of strong magnetic activity in the chromosphere. Measurement of periodic variations of these active regions can also be used to deduce the rotation periods of these stars.^[11]

Compounds

Calcium, combined with phosphate, forming hydroxylapatite, is the mineral portion of human and animal bones and teeth. The mineral portion of some corals can also be transformed into hydroxylapatite.^{[citation needed]}

Calcium forms a family of ionic compounds known as lime; they are all alkaline white powders (at STP). Calcium carbonate (CaCO₃) is one of the common compounds of calcium and occurs naturally as limestone and chalk. When heated at high temperature (above 825 °C), it forms calcium oxide (CaO), also known as quicklime. When added to water (H₂O), quicklime vigorously reacts (hence its name) to form calcium hydroxide (Ca(OH)₂). Also known as slaked lime, this substance is an inexpensive base material used throughout the chemical industry. When mixed with sand, it hardens into a mortar and is turned into plaster by carbon dioxide uptake. Mixed with other compounds, lime forms an important part of Portland cement.^{[citation needed]}

When water percolates through limestone or other soluble carbonate-containing rocks, it partially dissolves the rock and causes cave formation with their characteristic stalactites and stalagmites, and also forms hard water. Other important calcium compounds are calcium nitrate, calcium sulfide, calcium chloride, calcium carbide, calcium cyanamide and calcium hypochlorite.^{[citation needed]}

A few calcium compounds where calcium is in the oxidation state +1 have also been investigated recently.^[3] Charlotte Froese Fischer predicted that a Ca⁻ ion would be stable; this ion was discovered experimentally in 1987.^[12]

Isotopes

Calcium has five stable isotopes (⁴⁰Ca, ⁴²Ca, ⁴³Ca, ⁴⁴Ca and ⁴⁶Ca), plus one more isotope (⁴⁸Ca) that has such a long half-life that for all practical purposes it can also be considered stable. The 20% range in relative mass among naturally occurring calcium isotopes is greater than for any other element except hydrogen and helium. Calcium also has a cosmogenic isotope, radioactive ⁴¹Ca, which has a half-life of 103,000 years. Unlike cosmogenic isotopes that are produced in the atmosphere, ⁴¹Ca is produced by neutron activation of ⁴⁰Ca. Most of its production is in the upper metre or so of the soil column, where the cosmogenic neutron flux is still sufficiently strong. ⁴¹Ca has received much attention in stellar studies because it decays to ⁴¹K, a critical indicator of solar-system anomalies.^{[citation needed]}

Ninety-seven percent of naturally occurring calcium is in the form of ⁴⁰Ca. ⁴⁰Ca is one of the daughter products of ⁴⁰K decay, along with ⁴⁰Ar. While K–Ar dating has been used extensively in the geological sciences, the prevalence of ⁴⁰Ca in nature has impeded its use in dating. Techniques using mass spectrometry and a double spike isotope dilution have been used for K-Ca age dating.^{[citation needed]}

The most abundant isotope, ⁴⁰Ca, has a nucleus of 20 protons and 20 neutrons. This is the heaviest stable isotope of any element that has equal numbers of protons and neutrons. In supernova explosions, calcium is formed from the reaction of carbon with various numbers of alpha particles (helium nuclei), until the most common calcium isotope (containing 10 helium nuclei) has been synthesized.^{[citation needed]}

Isotope fractionation

As with the isotopes of other elements, a variety of processes fractionate, or alter the relative abundance of, calcium isotopes.^[13] The best studied of these processes is the mass-dependent fractionation of calcium isotopes that accompanies the precipitation of calcium minerals, such as calcite, aragonite and apatite, from solution. Isotopically light calcium is preferentially incorporated into minerals, leaving the solution from which the mineral precipitated enriched in isotopically heavy calcium. At room temperature the magnitude of this fractionation is roughly 0.25‰ (0.025%) per atomic mass unit (AMU). Mass-dependent differences in calcium isotope composition conventionally are expressed the ratio of two isotopes (usually ⁴⁴Ca/⁴⁰Ca) in a sample compared to the same ratio in a standard reference material. ⁴⁴Ca/⁴⁰Ca varies by about 1% among common earth materials.^[14]

Calcium isotope fractionation during mineral formation has led to several applications of calcium isotopes. In particular, the 1997 observation by Skulan and DePaolo^[15] that calcium minerals are isotopically lighter than the solutions from which the minerals precipitate is the basis of analogous applications in medicine and in paleooceanography. In animals with skeletons mineralized with calcium the calcium isotopic composition of soft tissues reflects the relative rate of formation and dissolution of skeletal mineral. In humans changes in the calcium isotopic composition of urine have been shown to be related to changes in bone mineral balance. When the rate of bone formation exceeds the rate of bone resorption, soft tissue ⁴⁴Ca/⁴⁰Ca rises. Soft tissue ⁴⁴Ca/⁴⁰Ca falls when bone resorption exceeds bone formation. Because of this relationship, calcium isotopic measurements of urine or blood may be useful in the early detection of metabolic bone diseases like osteoporosis.^[16]

A similar system exists in the ocean, where seawater ⁴⁴Ca/⁴⁰Ca tends to rise when the rate of removal of Ca²⁺ from seawater by mineral precipitation exceeds the input of new calcium into the ocean, and fall when calcium input exceeds mineral precipitation. It follows that rising ⁴⁴Ca/⁴⁰Ca corresponds to falling seawater Ca²⁺ concentration, and falling ⁴⁴Ca/⁴⁰Ca corresponds to rising seawater Ca²⁺ concentration. In 1997 Skulan and DePaolo presented the first evidence of change in seawater ⁴⁴Ca/⁴⁰Ca over geologic time, along with a theoretical explanation of these changes. More recent papers have confirmed this observation, demonstrating that seawater Ca²⁺ concentration is not constant, and that the ocean probably never is in “steady state” with respect to its calcium input and output.^[17]^[18] This has important climatological implications, as the marine calcium cycle is closely tied to the carbon cycle (see below).

Geochemical cycling

Calcium provides an important link between tectonics, climate and the carbon cycle. In the simplest terms, uplift of mountains exposes Ca-bearing rocks to chemical weathering and releases Ca²⁺ into surface water. This Ca²⁺ eventually is transported to the ocean where it reacts with dissolved CO₂ to form limestone. Some of this limestone settles to the sea floor where it is incorporated into new rocks. Dissolved CO₂, along with carbonate and bicarbonate ions, are referred to as dissolved inorganic carbon (DIC).

Travertine terraces Pamukkale, Turkey

The actual reaction is more complicated and involves the bicarbonate ion (HCO₃⁻) that forms when CO₂ reacts with water at seawater pH:

Ca2+
+ 2HCO−
3 → CaCO
3 (limestone) + CO
2 + H
2O

Note that at ocean pH most of the CO₂ produced in this reaction is immediately converted back into HCO−
3. The reaction results in a net transport of one molecule of CO₂ from the ocean/atmosphere into the lithosphere.^[19]

The result is that each Ca²⁺ ion released by chemical weathering ultimately removes one CO₂ molecule from the surficial system (atmosphere, ocean, soils and living organisms), storing it in carbonate rocks where it is likely to stay for hundreds of millions of years. The weathering of calcium from rocks thus scrubs CO₂ from the ocean and atmosphere, exerting a strong long-term effect on climate.^[20] Analogous cycles involving magnesium, and to a much smaller extent strontium and barium, have the same effect.

As the weathering of limestone (CaCO₃) liberates equimolar amounts of Ca²⁺ and CO₂, it has no net effect on the CO₂ content of the atmosphere and ocean. The weathering of silicate rocks like granite, on the other hand, is a net CO₂ sink because it produces abundant Ca²⁺ but very little CO₂.

History

'Ain Ghazal figure

Lime as building material was used since prehistoric times going as far back as 7000 to 14000 BC.^[21] Significant statues made from lime plaster date back into the 7 millennia BC were found in 'Ain Ghazal.^[22] The first dated lime kiln dates back to 2500 BC and was found in Khafajah mesopotamia.^[23]^[24] Calcium (from Latin calx, genitive calcis, meaning "lime")^[25] was known as early as the first century when the Ancient Romans prepared lime as calcium oxide. Literature dating back to 975 AD notes that plaster of paris (calcium sulfate), is useful for setting broken bones. It was not isolated until 1808 in England when Sir Humphry Davy electrolyzed a mixture of lime and mercuric oxide.^[26] Calcium metal was not available in large scale until the beginning of the 20th century.

Occurrence

Calcium is not naturally found in its elemental state. Calcium occurs most commonly in sedimentary rocks in the minerals calcite, dolomite and gypsum. It also occurs in igneous and metamorphic rocks chiefly in the silicate minerals: plagioclases, amphiboles, pyroxenes and garnets.

Applications

Calcium is used^[27]

as a reducing agent in the extraction of other metals, such as uranium, zirconium, and thorium.
as a deoxidizer, desulfurizer, or decarbonizer for various ferrous and nonferrous alloys.
as an alloying agent used in the production of aluminium, beryllium, copper, lead, and magnesium alloys.
in the making of cements and mortars to be used in construction.
in the making of cheese, where calcium ions influence the activity of rennin in bringing about the coagulation of milk.

Calcium compounds

Calcium carbonate (CaCO₃) is used in manufacturing cement and mortar, lime, limestone (usually used in the steel industry) and aids in production in the glass industry. It also has chemical and optical uses as mineral specimens in toothpastes, for example.
Calcium hydroxide solution (Ca(OH)₂) (also known as limewater) is used to detect the presence of carbon dioxide by being bubbled through a solution. It turns cloudy where CO₂ is present.
Calcium arsenate (Ca₃(AsO₄)₂) is used in insecticides.
Calcium carbide (CaC₂) is used to make acetylene gas (for use in acetylene torches for welding) and in the manufacturing of plastics.
Calcium chloride (CaCl₂) is used in ice removal and dust control on dirt roads, in conditioner for concrete, as an additive in canned tomatoes, and to provide body for automobile tires.
Calcium citrate (Ca₃(C₆H₅O₇)₂) is used as a food preservative.
Calcium cyclamate (Ca(C₆H₁₁NHSO₃)₂) is used as a sweetening agent in several countries. In the United States it is no longer permitted for use because of suspected cancer-causing properties.^[28]
Calcium gluconate (Ca(C₆H₁₁O₇)₂) is used as a food additive and in vitamin pills.
Calcium hypochlorite (Ca(OCl)₂) is used as a swimming pool disinfectant, as a bleaching agent, as an ingredient in deodorant, and in algaecide and fungicide.
Calcium permanganate (Ca(MnO₄)₂) is used in liquid rocket propellant, textile production, as a water sterilizing agent and in dental procedures.
Calcium phosphate (Ca₃(PO₄)₂) is used as a supplement for animal feed, fertilizer, in commercial production for dough and yeast products, in the manufacture of glass, and in dental products.
Calcium phosphide (Ca₃P₂) is used in fireworks, rodenticide, torpedoes and flares.
Calcium stearate (Ca(C₁₈H₃₅O₂)₂) is used in the manufacture of wax crayons, cements, certain kinds of plastics and cosmetics, as a food additive, in the production of water resistant materials and in the production of paints.
Calcium sulfate (CaSO₄·2H₂O) is used as common blackboard chalk, as well as, in its hemihydrate form better known as Plaster of Paris.
Calcium tungstate (CaWO₄) is used in luminous paints, fluorescent lights and in X-ray studies.
Hydroxylapatite (Ca₅(PO₄)₃(OH), but is usually written Ca₁₀(PO₄)₆(OH)₂) makes up seventy percent of bone. Also carbonated-calcium deficient hydroxylapatite is the main mineral of which dental enamel and dentin are comprised.

Nutrition

Recommended adequate intake by the IOM for calcium:^[29]^[30]
Age	Calcium (mg/day)
0–6 months	200
7–12 months	260
1–3 years	700
4–8 years	1000
9–18 years	1300
19–50 years	1000
51–70 years (male)	1000
51–70 years (female)	1200
71+ years	1200

Calcium is an important component of a healthy diet and a mineral necessary for life. The National Osteoporosis Foundation says, "Calcium plays an important role in building stronger, denser bones early in life and keeping bones strong and healthy later in life." Approximately 99 percent of the body's calcium is stored in the bones and teeth.^[31] The rest of the calcium in the body has other important uses, such as some exocytosis, especially neurotransmitter release, and muscle contraction. Intracellular calcium overload may lead some kind of cells to oxidative stress and apoptosis, and thus producing several diseases.^[32] In the electrical conduction system of the heart, calcium replaces sodium as the mineral that depolarizes the cell, proliferating the action potential. In cardiac muscle, sodium influx commences an action potential, but during potassium efflux, the cardiac myocyte experiences calcium influx, prolonging the action potential and creating a plateau phase of dynamic equilibrium. Long-term calcium deficiency can lead to rickets and poor blood clotting and in case of a menopausal woman, it can lead to osteoporosis, in which the bone deteriorates and there is an increased risk of fractures. While a lifelong deficit can affect bone and tooth formation, over-retention can cause hypercalcemia (elevated levels of calcium in the blood), impaired kidney function and decreased absorption of other minerals.^[33]^[34] Several sources suggest a correlation between high calcium intake (2000 mg per day, or twice the U.S. recommended daily allowance, equivalent to six or more glasses of milk per day) and prostate cancer.^[35] Vitamin D is needed to absorb calcium.

Dairy products, such as milk and cheese, are a well-known source of calcium. Some individuals are allergic to dairy products and even more people, in particular those of non Indo-European descent, are lactose-intolerant, leaving them unable to consume non-fermented dairy products in quantities larger than about half a liter per serving. Others, such as vegans, avoid dairy products for ethical and health reasons.

Many good vegetable sources of calcium exist, including seaweeds such as kelp, wakame, and hijiki; nuts and seeds like almonds, hazelnuts, sesame, and pistachio; blackstrap molasses; beans (especially soy beans); figs; quinoa; okra; rutabaga; broccoli; dandelion leaves; and kale. In addition, several foods and drinks, such as orange juice, soy milk, tofu, breakfast cereals, and breads are often fortified with calcium.^[36]

Numerous vegetables, notably spinach, chard, and rhubarb have a high calcium content, but they may also contain varying amounts of oxalic acid that binds calcium and reduces its absorption. The same problem may to a degree affect the absorption of calcium from amaranth, collard greens, and chicory greens. This process may also be related to the generation of calcium oxalate.

An overlooked source of calcium is eggshell, which can be ground into a powder and mixed into food or a glass of water.^[37]^[38]^[39]

The calcium content of most foods can be found in the USDA National Nutrient Database.^[40]

Dietary supplements

500 milligram calcium supplements made from calcium carbonate

Calcium supplements are used to prevent and to treat calcium deficiencies. Office of Dietary Supplements (National Institutes of Health) recommends that no more than 600 mg of supplement should be taken at a time because the percent of calcium absorbed decreases as the amount of calcium in the supplement increases.^[29] It is therefore recommended to spread doses throughout the day.^[41] Recommended daily calcium intake for adults ranges from 1000 to 1300 mg.^[41] Calcium supplements may have side effects such as bloating and constipation in some people. It is suggested that taking the supplements with food may aid in nullifying these side effects.^[41]

Vitamin D is added to some calcium supplements. Proper vitamin D status is important because vitamin D is converted to a hormone in the body, which then induces the synthesis of intestinal proteins responsible for calcium absorption.^[42]

The absorption of calcium from most food and commonly used dietary supplements is very similar.^[43] This is contrary to what many calcium supplement manufacturers claim in their promotional materials.
Milk is an excellent source of dietary calcium for those whose bodies tolerate it because it has a high concentration of calcium and the calcium in milk is excellently absorbed.^[43]
Soymilk and other vegetable milks are usually sold with calcium added so that their calcium concentration is as high as in milk.
Also different kind of juices boosted with calcium are widely available.
Calcium carbonate is the most common and least expensive calcium supplement. It should be taken with food, and depends on low pH levels (acidic) for proper absorption in the intestine.^[44] Some studies suggests that the absorption of calcium from calcium carbonate is similar to the absorption of calcium from milk.^[45]^[46]
Antacids frequently contain calcium carbonate, and are a commonly used, inexpensive calcium supplement.
Coral calcium is a salt of calcium derived from fossilized coral reefs. Coral calcium is composed of calcium carbonate and trace minerals.
Calcium citrate can be taken without food and is the supplement of choice for individuals with achlorhydria or who are taking histamine-2 blockers or proton-pump inhibitors.^[47] Calcium citrate is about 21% elemental calcium. 1000 mg will provide 210 mg of calcium. It is more expensive than calcium carbonate and more of it must be taken to get the same amount of calcium.
Calcium phosphate costs more than calcium carbonate, but less than calcium citrate. Microcrystalline Hydroxyapatite (MH) is one of several forms of calcium phosphate used as a dietary supplement. Hydroxyapatite is about 40% calcium.
Calcium lactate has similar absorption as calcium carbonate,^[48] but is more expensive. Calcium lactate and calcium gluconate are less concentrated forms of calcium and are not practical oral supplements.^[47]

Bone health

Calcium supplementation is generally not necessary for maintaining bone mineral density, and carries risks that outweigh any benefits.^[49] Calcium intake is not significantly associated with hip fracture risk in either men nor women.^[50] The U.S. Preventive Service Task Force therefore recommends against daily supplementation of calcium or Vitamin D.^[51]

Cardiovascular impact

A study investigating the effects of personal calcium supplement use on cardiovascular risk in the Women’s Health Initiative Calcium/Vitamin D Supplementation Study (WHI CaD Study) found a modestly increased risk of cardiovascular events, particularly myocardial infarction in postmenopausal women. A broad recommendation of calcium/vitamin D supplements is therefore not warranted.^[52] In contrast, the authors of a 2013 literature review concluded that the benefits of calcium supplementation, such as on bone health, appear to outweigh any risk calcium supplementation may theoretically pose to the cardiovascular health.^[53]

Cancer

Overall, there is no strong evidence calcium supplementation helps prevent cancer in people: some studies suggest it might decrease the risk, but others suggest it might increase the risk. The National Cancer Institute, part of the National Institutes of Health, does not recommend the use of calcium supplements to prevent any type of cancer, due to the lack of evidence supporting its use for this purpose.^[54]

There is weak evidence calcium supplementation might have a preventative effect against developing colorectal adenomatous polyps, but the evidence is insufficient to recommend such supplementation as a beneficial practice.^[55]

Cell signaling

The release of calcium ions from the sarcoplasmic reticulum into the cytoplasm is an essential intracellular signal, important in many cellular functions and processes, including muscle contraction, neuronal transmission as in an excitatory synapse, cellular motility (including the movement of flagella and cilia), fertilisation, cell growth or proliferation, learning and memory as with synaptic plasticity, and secretion of saliva.^[56]

Calcium signalling can be studied by loading a cell's cytoplasm with a calcium-sensitive fluorescent dye such as Fura-2.^[57]^[58] Many of these dyes were developed by Roger Y. Tsien.^{[citation needed]}

Hazards and toxicity

Compared with other metals, the calcium ion and most calcium compounds have low toxicity. This is not surprising given the very high natural abundance of calcium compounds in the environment and in organisms.

Calcium poses few serious environmental problems.

High calcium intakes or high calcium absorption were previously thought to contribute to the development of kidney stones. However, a high calcium intake has been associated with a lower risk for kidney stones in more recent research.^[59]^[60]^[61]

Acute calcium poisoning is rare, and difficult to achieve unless calcium compounds are administered intravenously. For example, the oral median lethal dose (LD⁵⁰) for rats for calcium carbonate and calcium chloride are 6.45^[62] and 1.4 g/kg,^[63] respectively.

Calcium metal is hazardous because of its sometimes-violent reactions with water and acids. Calcium metal is found in some drain cleaners, where it functions to generate heat and calcium hydroxide that saponifies the fats and liquefies the proteins (e.g., hair) that block drains. When swallowed calcium metal has the same effect on the mouth, esophagus and stomach, and can be fatal.^[64]

Excessive consumption of calcium carbonate antacids/dietary supplements (such as Tums) over a period of weeks or months can cause milk-alkali syndrome, with symptoms ranging from hypercalcemia to potentially fatal renal failure. What constitutes “excessive” consumption is not well known and, it is presumed, varies a great deal from person to person. Persons consuming more than 10 grams/day of CaCO₃ (=4 g Ca) are at risk of developing milk-alkali syndrome,^[65] but the condition has been reported in at least one person consuming only 2.5 grams/day of CaCO₃ (=1 g Ca), an amount usually considered moderate and safe.^[66]

Oral calcium supplements diminish the absorption of thyroxine when taken within four to six hours of each other.^[67] Thus, people taking both calcium and thyroxine run the risk of inadequate thyroid hormone replacement and thence hypothyroidism if they take them simultaneously or near-simultaneously.^[68]^{[unreliable medical source?]}

Although some studies have suggested that excessive intake of calcium in the diet or as supplements could be associated with increased cardiovascular mortality,^[69]^[70] other studies found no risk,^[71] leading a review to conclude that any risk could only be ascertained with specific further research.^[72]

References

^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 112. ISBN 0-08-037941-9.
^ Standard Atomic Weights 2013. Commission on Isotopic Abundances and Atomic Weights
^ ^a ^b Krieck, Sven; Görls, Helmar; Westerhausen, Matthias (2010). "Mechanistic Elucidation of the Formation of the Inverse Ca(I) Sandwich Complex [(thf)3Ca(μ-C6H3-1,3,5-Ph3)Ca(thf)3] and Stability of Aryl-Substituted Phenylcalcium Complexes". Journal of the American Chemical Society 132 (35): 12492–12501. doi:10.1021/ja105534w. PMID 20718434.
^ Dickson, A. G. & Goyet, C. (1994). "Chapter 5". Handbook of method for the analysis of the various parameters of the carbon dioxide system in sea water, version 2 (PDF). ORNL/CDIAC-74.
^ Pauling, Linus (1970). General Chemistry. Dover Publications. p. 627. ISBN 0-7167-0149-9.
^ Theodore Gray. The Elements. Page 55
^ http://education.jlab.org/itselemental/ele020.html
^ Bale, C. W.; Pelton, A. D. (1987). "The Ca−Li (Calcium-Lithium) system". Journal of Phase Equilibria 8 (2): 125–127. doi:10.1007/BF02873196.
^ Geoffrey Landis (2014). "Resource Production on the Moon" (PDF). NASA. Retrieved 2015-05-20.
^ Tordoff, M. G. (2001). "Calcium: Taste, Intake, and Appetite" (PDF). Physiological Reviews 81 (4): 1567–97. PMID 11581497.
^ Staff (1995). "H-K Project". Mount Wilson Observatory. Retrieved 2006-08-10.
^ Pegg, D. J.; Thompson, J. S.; Compton, R. N.; Alton, G. D. (1987). "Evidence for a stable negative ion of calcium". Phys. Rev. Lett. 59 (20): 2267–2270. Bibcode:1987PhRvL..59.2267P. doi:10.1103/PhysRevLett.59.2267.
^ Russell, WA; Papanastassiou, DA; Tombrello, TA (1978). "Ca isotope fractionation on the earth and other solar system materials". Geochim Cosmochim Acta 42 (8): 1075–90. Bibcode:1978GeCoA..42.1075R. doi:10.1016/0016-7037(78)90105-9.
^ Skulan, J; Depaolo, DJ (1999). "Calcium isotope fractionation between soft and mineralized tissues as a monitor of calcium use in vertebrates" (PDF). Proc Natl Acad Sci USA 96 (24): 13709–13. Bibcode:1999PNAS...9613709S. doi:10.1073/pnas.96.24.13709. PMC: 24129. PMID 10570137.
^ Skulan, J; Depaolo, DJ; Owens, TL (June 1997). "Biological control of calcium isotopic abundances in the global calcium cycle". Geochimica et Cosmochimica Acta 61 (12): 2505–10. Bibcode:1997GeCoA..61.2505S. doi:10.1016/S0016-7037(97)00047-1.
^ Skulan, J; Bullen, T; Anbar, AD; Puzas, JE; Shackelford, L; Leblanc, A; Smith, SM (2007). "Natural calcium isotopic composition of urine as a marker of bone mineral balance" (PDF). Clinical Chemistry 653 (6): 1155–1158. doi:10.1373/clinchem.2006.080143. PMID 17463176.
^ Fantle, M; Depaolo, D (2007). "Ca isotopes in carbonate sediment and pore fluid from ODP Site 807A: The Ca²⁺(aq)–calcite equilibrium fractionation factor and calcite recrystallization rates in Pleistocene sediments". Geochim Cosmochim Acta 71 (10): 2524–2546. Bibcode:2007GeCoA..71.2524F. doi:10.1016/j.gca.2007.03.006.
^ Griffith, Elizabeth M.; Paytan, Adina; Caldeira, Ken; Bullen, Thomas; Thomas, Ellen (2008). "A Dynamic marine calcium cycle during the past 28 million years". Science 322 (12): 1671–1674. Bibcode:2008Sci...322.1671G. doi:10.1126/science.1163614. PMID 19074345.
^ Zeebe (2006). "Marine carbonate chemistry". National Council for Science and the Environment. Retrieved 2010-03-13.
^ Berner, Robert (2003). "The long-term carbon cycle, fossil fuels and atmospheric composition". Nature 426 (6964): 323–326. Bibcode:2003Natur.426..323B. doi:10.1038/nature02131. PMID 14628061.
^ Miller, M. Michael. "Commodity report:Lime" (PDF). United States Geological Survey. Retrieved 2012-03-06.
^ Garfinkel, Yosef (1987). "Burnt Lime Products and Social Implications in the Pre-Pottery Neolithic B Villages of the Near East". Paléorient 13 (1): 69–76. doi:10.3406/paleo.1987.4417. JSTOR 41492234.
^ Williams, Richard (2004). Lime Kilns and Lime Burning. p. 4. ISBN 978-0-7478-0596-0.
^ Oates, J. A. H (2008-07-01). Lime and Limestone: Chemistry and Technology, Production and Uses. ISBN 978-3-527-61201-7.
^ calx. Charlton T. Lewis and Charles Short. A Latin Dictionary on Perseus Project.
^ Davy H (1808). "Electro-chemical researches on the decomposition of the earths; with observations on the metals obtained from the alkaline earths, and on the amalgam procured from ammonia". Philosophical Transactions of the Royal Society of London 98: 333–370. Bibcode:1808RSPT...98..333D. doi:10.1098/rstl.1808.0023.
^ Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
^ Newton, David E (2009-01-01). Food Chemistry. pp. 73–77. ISBN 9781438109756.
^ ^a ^b "Dietary Supplement Fact Sheet: Calcium". Retrieved 2011-03-08.
^ "Dietary Reference Intakes for Calcium and Vitamin D" (PDF). November 2010.
^ "Dietary Supplement Fact Sheet: Calcium". Office of Dietary Supplements, NIH. Retrieved 2011-03-31.
^ Espino J, Bejarano I, Paredes SD, González D, Barriga C, Reiter RJ, Pariente JA, Rodríguez AB (January 2010). "Melatonin Counteracts Altrations in Oxidative Metabolism and Cell Viability Induced by Intracellular Calcium Overload in Human Leucocytes: Changes with Age". Basic & Clinical Pharmacology & Toxicology 107: 590-597. doi:[10.1111/j.1742-7843.2010.00546.x]
^ Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, Food and Nutrition Board, Institute of Medicine (1997). Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D and fluoride. Washington DC: The National Academies Press. ISBN 0-309-06403-1.
^ Committee to Review Dietary Reference Intakes for Vitamin D and Calcium; Institute of Medicine (2011). A. Catharine Ross; Christine L. Taylor; Ann L. Yaktine; Heather B. Del Valle, eds. Dietary Reference Intakes for Calcium and Vitamin D. ISBN 978-0-309-16394-1.
^ Giovannucci E; Rimm EB; Wolk A; et al. (February 1998). "Calcium and fructose intake in relation to risk of prostate cancer". Cancer Research 58 (3): 442–7. PMID 9458087.
^ "Calcium in Diet". Retrieved 14 September 2014.
^ Schaafsma, Anne & Beelen, Gerard M (1999). "Eggshell powder, a comparable or better source of calcium than purified calcium carbonate: piglet studies". Journal of the Science of Food and Agriculture 79 (12): 1596–1600. doi:10.1002/(SICI)1097-0010(199909)79:12<1596::AID-JSFA406>3.0.CO;2-A.
^ Schaafsma A; van Doormaal JJ; Muskiet FA; Hofstede GJ; Pakan I; van der Veer E (2002). "Positive effects of a chicken eggshell powder-enriched vitamin-mineral supplement on femoral neck bone mineral density in healthy late post-menopausal Dutch women". Br. J. Nutr. 87 (3): 267–75. doi:10.1079/BJNBJN2001515. PMID 12064336.
^ Rovenský J; Stancíková M; Masaryk P; Svík K; Istok R (2003). "Eggshell calcium in the prevention and treatment of osteoporosis". Int J Clin Pharmacol Res 23 (2–3): 83–92. PMID 15018022.
^ "USDA National Nutrient Database". Archived from the original on 23 August 2015.
^ ^a ^b ^c "Dietary Supplement Fact Sheet: Calcium – Quick Facts — Retrieved 2013-08-23
^ Combs, G (2008). The Vitamins. Academic Press. p. 161. ISBN 0-12-183490-5.
^ ^a ^b Weaver, CM (2006). "29 Calcium". In Barbara A. Bowman; Robert M. Russell. Present Knowledge in Nutrition I (9th ed.). ILSI Press. p. 377. ISBN 1-57881-198-8.
^ Remington, Joseph (2005). Remington: The Science and Practice of Pharmacy. Lippincott Williams & Wilkins. p. 1338. ISBN 0-7817-4673-6.
^ Zhao, Y; Martin, BR; Weaver, CM (2005). "Calcium bioavailability of calcium carbonate fortified soy milk is equivalent to cow's milk in young women" (PDF). J. Nutr. 135 (10): 2379–82. PMID 16177199.
^ Martini, Ligia & Wood, Richard J (2002). "Relative bioavailability of calcium-rich dietary sources in the elderly" (PDF). American Journal of Clinical Nutrition 76 (6): 1345–1350. PMID 12450902.
^ ^a ^b Straub, D. A. (2007). "Calcium Supplementation in Clinical Practice: A Review of Forms, Doses, and Indications". Nutrition in Clinical Practice 22 (3): 286–96. doi:10.1177/0115426507022003286. PMID 17507729.
^ Martin, Berdine R.; Weaver, CM; Heaney, RP; Packard, PT; Smith, DL (2002). "Calcium Absorption from Three Salts and CaSO₄-Fortified Bread in Premenopausal Women". Journal of Agricultural and Food Chemistry 50 (13): 3874–6. doi:10.1021/jf020065g. PMID 12059174.
^ Reid IR, Bristow SM, Bolland MJ (2015). "Calcium supplements: benefits and risks". J. Intern. Med. (Review) 278: 354–68. doi:10.1111/joim.12394. PMID 26174589.
^ Bischoff-Ferrari, Heike A.; Dawson-Hughes, Bess; Baron, John A.; Burckhardt, Peter; Li, Ruifeng; Spiegelman, Donna; Specker, Bonny; Orav, John E.; Wong, John B. (2007-12-01). "Calcium intake and hip fracture risk in men and women: a meta-analysis of prospective cohort studies and randomized controlled trials". The American Journal of Clinical Nutrition 86 (6): 1780–1790. ISSN 0002-9165. PMID 18065599.
^ Moyer, Virginia A. (2013-05-07). "Vitamin D and calcium supplementation to prevent fractures in adults: U.S. Preventive Services Task Force recommendation statement". Annals of Internal Medicine 158 (9): 691–696. doi:10.7326/0003-4819-158-9-201305070-00603. ISSN 1539-3704. PMID 23440163.
^ M. J. Bolland, A. Grey, A. Avenell, G. D. Gamble, I. R. Reid. (2011). "Calcium supplements with or without vitamin D and risk of cardiovascular events: reanalysis of the Women's Health Initiative limited access dataset and meta-analysis." BMJ;342:d2040 DOI: 10.1136/bmj.d2040
^ Downing L; Islam MA (July 2013). "Influence of calcium supplements on the occurrence of cardiovascular events". Am J Health Syst Pharm (Review) 70 (13): 1132–9. doi:10.2146/ajhp120421. PMID 23784160.
^ "Calcium and Cancer Prevention: Strengths and Limits of the Evidence". National Cancer Institute. 4 May 2009. Retrieved November 2014.
^ Weingarten MA; Zalmanovici A; Yaphe J (2008). "Dietary calcium supplementation for preventing colorectal cancer and adenomatous polyps". Cochrane Database Syst Rev (Review) (1): CD003548. doi:10.1002/14651858.CD003548.pub4. PMID 18254022.
^ Berridge, Michael J.; Lipp, Peter; Bootman, Martin D. (October 2000). "The versatility and universality of calcium signalling". Nature Reviews Molecular Cell Biology 1 (1): 11–21. doi:10.1038/35036035. PMID 11413485.
^ D. González, I. Bejarano, C. Barriga, A.B. Rodríguez, J.A. Pariente (2010). "Oxidative Stress-Induced Caspases are Regulated in Human Myeloid HL-60 Cells by Calcium Signal". Current Signal Transduction Therapy 5: 181-186. doi:[10.2174/157436210791112172]
^ Bejarano I, Espino J, González-Flores D, Casado JG, Redondo PC, Rosado JA, Barriga C, Pariente JA, Rodríguez AB (2009). "Role of Calcium Signals on Hydrogen Peroxide-Induced Apoptosis in Human Myeloid HL-60 Cells". International Journal of Biomedical science 5(3): 246-256.
^ Curhan, GC; Willett, WC; Rimm, EB; Stampfer, MJ (1993). "A prospective study of dietary calcium and other nutrients and the risk of symptomatic kidney stones" (PDF). The New England Journal of Medicine 328 (12): 833–8. doi:10.1056/NEJM199303253281203. PMID 8441427.
^ Bihl G; Meyers A. (2001). "Recurrent renal stone disease-advances in pathogenesis and clinical management". Lancet 358 (9282): 651–656. doi:10.1016/S0140-6736(01)05782-8. PMID 11530173.
^ Hall WD; Pettinger M; Oberman A (2001). "Risk factors for kidney stones in older women in the Southern United States". Am J Med Sci 322 (1): 12–18. doi:10.1097/00000441-200107000-00003. PMID 11465241.
^ Lewis, R. J. (1996). Sax's Dangerous Properties of Industrial Materials (9th ed.). New York, NY: Van Nostrand Reinhold. p. 635. ISBN 0-471-37858-5.
^ ITII. Toxic and Hazardous Industrial Chemicals Safety Manual. Tokyo, Japan: The International Technical Information Institute. 1988. p. 101.
^ Rumack BH. POISINDEX. Information System Micromedex, Inc., Englewood, CO, 2010; CCIS Volume 143. Hall AH and Rumack BH (Eds)
^ Beall DP; Henslee HB; Webb HR; Scofield RH (2006). "Milk-alkali syndrome: a historical review and description of the modern version of the syndrome". Am. J. Med. Sci. 331 (5): 233–42. doi:10.1097/00000441-200605000-00001. PMID 16702792.
^ Picolos MK & Orlander PR (2005). "Calcium carbonate toxicity: The updated milk-alkali syndrome; report of 3 cases and review of the literature". Endocrine Practice 4 (11): 272–80. doi:10.4158/EP.11.4.272. PMID 16006300.
^ Singh, N.; Singh, P.; Hershman, J. (2000). "Effect of calcium carbonate on the absorption of levothyroxine". JAMA: the Journal of the American Medical Association 283 (21): 2822–2825. doi:10.1001/jama.283.21.2822. PMID 10838651.
^ Harding, Anne. "Calcium May Help With Weight Loss". Retrieved 2007-07-10.
^ Michaëlsson K; Melhus H; Warensjö Lemming E; Wolk A; Byberg L (2013). "Long term calcium intake and rates of all cause and cardiovascular mortality: community based prospective longitudinal cohort study". BMJ 346: f228. doi:10.1136/bmj.f228. PMC: 3571949. PMID 23403980.
^ Xiao Q; Murphy RA; Houston DK; Harris TB; Chow WH; Park Y (2013). "Dietary and supplemental calcium intake and cardiovascular disease mortality: the National Institutes of Health-AARP diet and health study". JAMA Internal Medicine 173 (8): 639–646. doi:10.1001/jamainternmed.2013.3283. PMC: 3756477. PMID 23381719.
^ Paik JM, Curhan GC, Sun Q, et al. (2014). "Calcium supplement intake and risk of cardiovascular disease in women". Osteoporos Int 25 (8): 2047–56. doi:10.1007/s00198-014-2732-3. PMC: 4102630. PMID 24803331.
^ Waldman T, Sarbaziha R, Merz CN, Shufelt C (2015). "Calcium Supplements and Cardiovascular Disease: A Review". Am J Lifestyle Med 9 (4): 298–307. doi:10.1177/1559827613512593. PMC: 4560115. PMID 26345134.

External links

WebElements.com – Calcium
Calcium at The Periodic Table of Videos (University of Nottingham)
UK Food Standards Agency: Calcium
Nutrition fact sheet from the National Institutes of Health

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

1. 骨粗鬆症におけるカルシウムおよびビタミンDの補充 calcium and vitamin d supplementation in osteoporosis
2. Calcium: Drug formulations (oral and parenteral)
3. 思春期におけるカルシウムの所要量 calcium requirements in adolescents
4. カルシウムおよびリン酸バランスの調節 regulation of calcium and phosphate balance
5. 総血清カルシウムとイオン化血清カルシウム濃度の相関 relation between total and ionized serum calcium concentrations

English Journal

Evaluation of osteoporosis risk and initiation of a nurse practitioner intervention program in an orthopedic practice.

Seuffert P1, Sagebien CA2, McDonnell M2, O Hara DA2.
Archives of osteoporosis.Arch Osteoporos.2016 Dec;11(1):10. doi: 10.1007/s11657-016-0262-7. Epub 2016 Feb 4.
The purpose of this study was to assess whether education and referral by a nurse practitioner could improve treatment adherence in patients with low bone mineral density in the orthopedic office. Our customized project did show some improvement but resistance to care continues in this unique popula
PMID 26847628

Bilateral non-traumatic hip fractures in a heavy smoker COPD patient on inhaled steroids.

Sanel S1, Sezgin G2, Sarıman N3, Ugutmen E1, Solakoglu C1.
Archives of osteoporosis.Arch Osteoporos.2016 Dec;11(1):8. doi: 10.1007/s11657-016-0259-2. Epub 2016 Jan 18.
INTRODUCTION: Bilateral proximal femoral fractures without trauma are very rare conditions. They have been reported in connection with osteoporosis, renal osteodystrophy, parathyroid disease, tumors, epileptic seizures, electroconvulsive therapy, and postirradiation.METHOD: We present a case of a 75
PMID 26781126

The role of childhood trauma in bipolar disorders.

Aas M1,2,3, Henry C4,5,6,7,8, Andreassen OA9,10,11, Bellivier F12,13,14, Melle I15,16,17, Etain B18,19,20,21.
International journal of bipolar disorders.Int J Bipolar Disord.2016 Dec;4(1):2. doi: 10.1186/s40345-015-0042-0. Epub 2016 Jan 13.
This review will discuss the role of childhood trauma in bipolar disorders. Relevant studies were identified via Medline (PubMed) and PsycINFO databases published up to and including July 2015. This review contributes to a new understanding of the negative consequences of early life stress, as well
PMID 26763504

Heterologous Expression and Functional Analysis of Rice GLUTAMATE RECEPTOR-LIKE Family Indicates its Role in Glutamate Triggered Calcium Flux in Rice Roots.

Ni J1, Yu Z2, Du G3, Zhang Y4, Taylor JL5, Shen C6, Xu J7, Liu X8, Wang Y9, Wu Y10.
Rice (New York, N.Y.).Rice (N Y).2016 Dec;9(1):9. doi: 10.1186/s12284-016-0081-x. Epub 2016 Mar 8.
BACKGROUND: Tremendous progress has been made in understanding the functions of the GLUTAMATE RECEPTOR-LIKE (GLR) family in Arabidopsis. Still, the functions of OsGLRs in rice, especially the ion channel activities, are largely unknown.RESULTS: Using the aequorin-based luminescence imaging system, w
PMID 26956369

Japanese Journal

Museum archives of the 19 years long time-series sediment trap samples collected at central subarctic Pacific Station SA and Bering Sea Station AB during 1990-2010

Takahashi Kozo,Asahi Hirofumi,Okazaki Yusuke,Onodera Jonaotaro,Tsutsui Hideto,Ikenoue Takahito,Kanematsu Yoshiyuki,Tanaka Seiji,Iwasaki Shinya,高橋孝三,朝日博史,岡崎裕典,小野寺丈尚太郎,筒井英人,池上隆仁,兼松芳幸,田中聖二,岩崎晋弥,タカハシコウゾウ,アサヒヒロフミ,オカザキユウスケ,オノデラジョウナオタロウ,ツツイヒデト,イケノウエタカヒト,カネマツヨシユキ,タナカセイジ,イワサキシンヤ
Memoirs of the Faculty of Science, Kyushu University. Series D, Earth and planetary sciences 32(4), 1-39, 2012-03-01
… and geochemical aspects of chemical compounds such as biogenic opal, calcium carbonate and hexosamine as well as elements such as rare earth elements. …
NAID 120003837079

In vitro evaluation of calcium alginate gels as matrix for iontophoresis electrodes

Haida Haruka,Ando Shizuka,Ogami Saori,Wakita Ryo,Kohase Hikaru,Saito Norio,Yoshioka Tomohiko,Ikoma Toshiyuki,Tanaka Junzo,Umino Masahiro,Fukayama Haruhisa
Journal of medical and dental sciences 59(1), 9-16, 2012-03
NAID 110008904364

附属学校における科学教育研究実践の効果とその評価Ⅱ―天王寺地区附属学校におけるPISA2006調査項目に基づく学年推移調査―

仲矢史雄,片桐昌直,畦浩二,なかやふみお,かたぎりまさなお,うねこうじ,NAKAYA Fumio,KATAGIRI Masanao,UNE Koji
大阪教育大学紀要　第Ⅳ部門　教育科学 60(2), 69-76, 2012-02-29
附属学校において実施されている科学教育活動の実践効果を捉えるため，PISA2006調査に採用されたアンケート項目を用いて，天王寺地区附属学校児童，生徒を対象に調査を行った。科学に関する認識や関心は，学年が進むにつれて，徐々に減少する傾向が示された。各学年の前期と後期の結果から，関心の向上の低下と回復が繰り返されていた。環境問題や社会における科学の価値など，小学校の時点から高い水準を示している項目は …
NAID 120003933900

Related Pictures

★リンクテーブル★

リンク元	「100Cases 14」「100Cases 27」「カルシウム」「100Cases 16」「Ca」
拡張検索	「dicalcium phosphate anhydrous」「calcium deficiency」「calcium current」「monobasic calcium phosphate」「calcium-containing stone」

「100Cases 14」

Calcium, ₂₀Ca
	Spectral lines of calcium
General properties
Name, symbol	calcium, Ca
Appearance	dull gray, silver; with a pale yellow tint
Pronunciation	/ˈkælsiəm/; KAL-see-əm
Calcium in the periodic table
	potassium ← calcium → scandium
Atomic number (Z)	20
Group, block	group 2 (alkaline earth metals), s-block
Period	period 4
Element category	alkaline earth metal
Standard atomic weight (±) (Ar)	40.078(4)
Electron configuration	[Ar] 4s2
per shell	2, 8, 8, 2
Physical properties
Phase	solid
Melting point	1115 K (842 °C, 1548 °F)
Boiling point	1757 K (1484 °C, 2703 °F)
Density near r.t.	1.55 g/cm3
when liquid, at m.p.	1.378 g/cm3
Heat of fusion	8.54 kJ/mol
Heat of vaporization	154.7 kJ/mol
Molar heat capacity	25.929 J/(mol·K)
Atomic properties
Oxidation states	+2, +1, −1 (a strongly basic oxide)
Electronegativity	Pauling scale: 1.00
Ionization energies	1st: 589.8 kJ/mol; 2nd: 1145.4 kJ/mol; 3rd: 4912.4 kJ/mol; (more)
Atomic radius	empirical: 197 pm
Covalent radius	176±10 pm
Van der Waals radius	231 pm
Miscellanea
Crystal structure	face-centered cubic (fcc)
Speed of sound thin rod	3810 m/s (at 20 °C)
Thermal expansion	22.3 µm/(m·K) (at 25 °C)
Thermal conductivity	201 W/(m·K)
Electrical resistivity	33.6 nΩ·m (at 20 °C)
Magnetic ordering	diamagnetic
Young's modulus	20 GPa
Shear modulus	7.4 GPa
Bulk modulus	17 GPa
Poisson ratio	0.31
Mohs hardness	1.75
Brinell hardness	170–416 MPa
CAS Number	7440-70-2
History
Discovery and first isolation	Humphry Davy (1808)
Most stable isotopes of calcium
	Decay modes in parentheses are predicted, but have not yet been observed
	view; talk; edit; \| references

　　[★]

☆case14　複視

■glossary

diplopia n. 複視

筋力低下、筋無力、筋脱力 muscle weakness, muscular weakness

sunken

vt. sinkのpp.

adj.

沈没した、沈んだ、水中の

沈下した、一段低いところにある

落ち込んだ、くぼんだ

3,4-ジアミノピリジン 3,4-diaminopyridine 3,4-DAP K+チャネル阻害薬;ランバート・イートン筋無力症治療

■症例

43-year-old woman

cheif complaint: diplopia

present history: diplopia and holding her head up ; more marked in the evenings, for the last 3 months. difficulty of chewing. voice has become quieter. weight loss (3kg / 6months). non-smoker. drinks about 15 units/week. no regular medication.

past history: no significant previous medical illnesses.

family history: lives with her husband and three children.

・診察 examination

looks well.

organ systems: normal; cardiovascular, respiratory, and abdominal systems.

muscle power; grossly normal. decrease after testing a movement repetitively.

motor function: normal; tone, coordination, reflexes and sensation.

bilateral ptosis. exacerbated by prolonged upward gaze

eye: normal; pupillary reflexes, eye movements, and funduscopy

■答え

diagnosis: myathenia gravis

differential diagnoses:

CASES

上位and/or下位運動ニューロン motor neurone disease　運動ニューロン疾患：線維束性攣縮。進行例では筋力低下

筋 muscular dystrophy　筋ジストロフィー：ある種の筋肉が選択的に筋力低下する。家族歴がある。

筋 dystrophia myotonica　強直性筋ジストロフィー：咬筋、側頭筋、胸鎖乳突筋の筋萎縮、四肢遠位端の筋萎縮。顔貌が特徴的(前頭部脱毛、無表情、窪んだ頬)。家族歴ある。筋電図が診断に有用(急降下爆撃音)。

筋 polymyositis　多発筋炎：普通は皮疹と関節痛が出現。CKが上昇。筋生検が診断に有用

筋 myopathy　ミオパチー：甲状腺中毒性ミオパチー、甲状腺機能低下症によるミオパチー、クッシング症候群によるミオパチー、アルコール性のミオパチー

神経筋接合部？ non-metastatic associations of malignancy (paraneoplastic syndrome(傍腫瘍性症候群 = 腫瘍随伴症候群)のこと)：胸腺腫の症例の10%に重症筋無力症がみられる。ランバート・イートン筋無力症症候群は小細胞癌と関連がある。

HIM.2674

神経筋接合部 congenital myasthenia syndrome　先天性筋無力症症候群
神経筋接合部 drug-induced myasthenia　薬剤性筋無力症

Treatment with penicillamine (used for scleroderma or rheumatoid arthritis) may result in true autoimmune MG, but the weakness is usually mild, and recovery occurs within weeks or months after discontinuing its use.

　重症筋無力症の誘発：ペニシラミン(強皮症や関節リウマチの治療に用いられる)。

　　mildだし、薬剤の中断で改善する。

Aminoglycoside antibiotics or procainamide can cause exacerbation of weakness in myasthenic patients; very large doses can cause neuromuscular weakness in normal individuals.

　重症筋無力症の悪化：アミドグリコシド系抗菌薬、プロカインアミド

　　MGの患者の筋脱力が悪化する。

神経筋接合部 Lambert-Eaton myasthenic syndrome　ランバート・イートン筋無力症症候群：全身の筋肉が冒されるが、特に下肢の近位筋が冒される。MGと同じように～70%の患者で脳神経所見(眼瞼下垂、複視など)が認められる。MGと違うのは(1)反射が消失・減弱すること、(2)自律神経系の変化(口渇、勃起不全)を生じる、(3)神経刺激検査で漸増(waxing)が見られることである。病因は神経筋接合部のP/Q type calcium channelsに対する抗体の出現であり、85%の患者で見いだされる。治療はMGのように血漿交換や免疫抑制薬が使われる。3,4-DAPやpyridostigmineは症状に対する治療のために用いる。前者は運動神経の終末部でカルシウムチャネルをブロックし活動電位を延長させる。後者はアセチルコリンエステラーゼを阻害してシナプスにおける神経伝達物質の濃度を上げる。
精神疾患 neurasthenia　神経衰弱症：歴史的な用語。器質的な障害を伴わない筋無力症のような脱力を伴う症候群。患者は筋脱力や疲労を訴えてやってくる。筋肉の検査では器質的変化は認めないが"jerky release"あるいは"give-away weakness"が認められる。患者の主訴は反復動作による筋力低下よりむしろ疲労や感情鈍麻である。
内分泌疾患 hyperthyroidism　甲状腺機能亢進症：MGが疑われる患者にはthyroid function testをルーチンにやる。甲状腺機能異常は筋無力症の筋力低下を大きくすることがある。
神経筋接合部 botulism　ボツリヌス症：ボツリヌス毒素はシナプス前膜からの神経伝達物質の開口分泌を妨げる。症状はbulbar weakness (複視、構音障害、嚥下困難)。感覚障害はない。深部腱反射は初期には保たれている。進行すれば反射は見られなくなる。筋脱力は全身性。呼吸困難に陥ることがある。精神状態は正常。自律神経症状(麻痺性イレウス、便秘、urinary retention、瞳孔の散大、瞳孔の反応性低下、口渇)。確定診断は血清中の毒素の検出だけど、見つかることはまれ。神経伝導検査(nerve conduction studies)：compound muscle action potentials (CMAPs)の低下。高頻度の刺激で振幅が増加。治療：intubation for airway protection、呼吸補助、aggressive inpatient supportive care(e.g., nutrition, DVT prophylaxis)。馬の抗毒素を検査結果が帰ってくる前に投与する(？)。
上位運動ニューロン intracranial mass lesions　頭蓋内占拠病変：複視はintracranial mass lesionが外眼筋の神経を圧迫することにより生じる。
筋 progressive external ophthalmoplegia　進行性外眼筋麻痺：外眼筋の筋脱力を伴う。四肢の近位筋の筋力低下やそのほかの全身症状を伴うことがある。ミトコンドリアの異常を有する。

■参考文献

HIM = Harrison's Principles of Internal Medicine 17th Edition

CASES = 100 Cases in Clinical Medicine Second edition

IMD = 内科診断学第2版

「100Cases 27」

　　[★]

☆case27　関節痛

■症例

37歳　女性

主訴：関節痛

現病歴：数ヶ月、膝の痛みがだんだん強くなっていると感じていた。痛みは手や足の小関節に多く、朝歩くときに最もこわばる。痛みはジクロフェナクを飲むと和らぐ。そのほかの症状として疲労感を感じ、最近、体重が３ヶ月で４ｋｇ減っている。

喫煙歴：なし。

飲酒歴：機会飲酒

既往歴：なし

家族歴：既婚、子供は２人

服薬歴：ジクロフェナク

職業歴：legal sevretary

身体所見 examination

　顔貌　青白、臨床的な貧血を認める。近位指節間関節・中手指節関節　腫脹・effusionを伴う疼痛。中足趾節関節　圧痛。それ以外は正常。

検査　 investigation

　血液検査

　　Hb低下

　　ESR 上昇

　　尿素軽度上昇

　　クレアチニン軽度上昇

　　正常：白血球、MCV、血小板、ナトリウム、カリウム、グルコース、アルブミン

　尿検査

　　蛋白(-)、尿糖(-)、潜血(-)、

■問題

　本症例では診断とその根拠を考えるのは簡単なので、鑑別疾患をあげてその疾患に特徴的な症候を列挙しましょう。

■関節痛 DIF.283

　V Vascular

　　血友病 hemophilia　血友病性関節症(急性：疼痛、腫脹、熱感(SOR.241)

慢性：可動域の低下、変形、関節周囲筋萎縮(SOR.241))。家族歴

　　壊血病 scurvy　。生活環境。食事歴

　　無菌性骨壊死 aseptic bone necrosis (Osgood-Schlatter diseaseとか)

　I Inflammatory

　　感染性関節炎(細菌性関節炎(化膿性関節炎・淋菌性関節炎・結核性関節炎・嫌気性菌関節炎 )、真菌性関節炎、スピロヘータ関節炎(梅毒性関節炎・ライム関節炎)、マイコプラズマ関節炎、ウイルス性関節炎)

　N Neoplastic disorders

　　骨原性肉腫 osteogenic sarcoma

　　巨細胞腫 giant cell tumors

　D Degenerative disorders

　　degenerative joint disease

　　変形性関節症 osteoarthritis

　I Intoxication

　　痛風 gout (uric acid)

　　偽痛風 pseudogout (calcium pyrophosphate)

　　ループス症候群 lupus syndrome of hydralazine (Apresoline) and procainamide

　　gout syndrome of diuretics

　C Congenital and acquired malformations bring to mind the joint deformities of tabes dorsalis and syringomyelia and congenital dislocation of the hip. Alkaptonuria is also considered here.

　A Autoimmune indicates

　　関節リウマチ RA

　　血清病 serum sickness

　　全身性エリテマトーデス lupus erythematosus

　　リウマチ熱 rheumatic fever

　　ライター症候群 Reiter syndrome

　　潰瘍性大腸炎 ulcerative colitis

　　クローン病=限局性回腸炎 regional ileitis

　　乾癬性関節炎 psoriatic arthritis

　　リウマチ性多発筋痛症 polymyalgia rheumatica

　T Trauma

　E Endcrine

　　先端肥大症 acromegaly

　　閉経 menopause

　　糖尿病 diabetes mellitus

■関節炎の分類

・炎症部位の数

　単関節炎：痛風、偽痛風、離断性骨軟骨炎、血行性の化膿性関節炎のほとんど

　多関節炎：リウマチ性疾患、ウイルス性疾患、白血病での関節症状、易感染性宿主における血行性の化膿性関節炎

■関節リウマチ

　診断基準

　関節症状

　　朝のこわばり、疼痛、腫脹、関節の動揺、関節可動域制限、変形(手指、足趾、膝関節)。(SOR.211)

　　手指の近位指節間関節(PIP 関節)、中手指節関節(MP 関節)。遠位指節間関節(DIP 関節)に初発することは稀。(SOR.211)

　　左右対称性に生じることが多い。手関節、足趾、膝関節に初発する。(SOR.211)

　関節外症状

　　全身症状：発熱

　　皮膚症状：リウマトイド結節(肘の伸側、後頭部、手指)

　　眼症状：上胸膜炎(10日の経過で治癒)、強膜炎(予後不良)。稀に角膜穿孔

　　血液障害：(高頻度)貧血、白血球減少(Felty病。DMARDs投与中の場合は薬剤性の骨髄抑制を考慮)

　　アミロイドーシス：ネフローゼや下痢を来した症例で疑う。アミロイド蛋白はAA

　　腎障害：稀。アミロイドーシスの続発症か薬剤性を考慮。

　　呼吸器症状：間質性肺炎の合併多い。下肺野に好発。通常無症状。メトトレキセートなどの使用により薬剤性の急性間質性肺炎を生じることがある。

　　心・血管障害：リンパ管炎による難治性の浮腫。

　　神経症状：環軸関節亜脱臼により項部痛や脊髄症上が出現しうる。

　　骨粗鬆症

　　腱鞘滑膜炎：手指、手関節、足関節

■両側性多関節炎の鑑別疾患

　OA：遠位指節間関節を冒すのが特徴的で、近位指節間関節、中手指節関節を冒しうる。

　RA：

　SLE：軽度、症状の程度が変動する非びらん性の関節炎

　gout：単関節炎からはじまる。

　血清陰性関節炎：強直性脊椎炎、感染、ライター病：中～大関節に非対称性の関節炎。仙腸関節と遠位指節間関節にも関節炎

　急性ウイルス性関節炎：風疹。

■KEY POINTS

・RAでは遠位指節間関節は冒されない傾向がある。

・RAの全身症状は関節症状に先行することがある。

・RAの活動性と貧血及びESRは相関している。

・NSAIDsは腎機能に悪影響を与えることがある。

■initial plan

　Dx 1. 単純X線写真

　　　　・亜脱臼、関節周囲の骨萎縮(傍関節性骨骨粗鬆症,juxta-articular osteoporosis)、関節裂隙の狭小化、関節辺縁のびらん(bony erosion)

　　　　　・初期のRAで第5趾に骨びらんが一般的に見られる。

　　　　・血液検査

　　　　　・RF、抗DNA 抗体

　Tx 1. 鎮痛薬

　　　　・NSAIDs：鎮痛とこわばりの軽減

　　 2. DMARDs(メトトレキセート、レフルノミド、金製剤、ペニシラミン)

　　　　・NSAIDsで症状が治まらない場合に考慮

　　 3. 抗TNF 抗体

　　　　・重症のRAで効果がある場合がある。

■参考文献

SOR　標準整形外科学第10版医学書院

DIF　Differential Diagnosis in Primary Care Fourth Edition版 Lippincott Williams & Wilkins

「カルシウム」

　　[★]

英: calcium
関: カルシウムイオン、リン; calcium channel blockers, calcium channels

基準値

血清総Ca 8.6-10.1 mg/dl(臨床検査法提要第32版)
8.6-10.2 mg/dL (QB)　　　だいたい　　9.4 ± 0.8
血清Caイオン 1.15-1.30 mmmol/l(臨床検査法提要第32版), 4.6-5.1 mg/dl

血液ガス

血液ガスでは (mEq/l)で出されるが 4倍すれば (mg/dl)に変換できる　　原子量が約40ゆえ

溶解度積

http://taniwa.hp.infoseek.co.jp/gyunyu/no9.html

リン酸カルシウム	366x10^-6	（30℃）
リン酸カルシウム	0.35x10^-6	（38℃）
炭酸カルシウム	0.0087x10^-6	（25℃）
酒石酸カルシウム	0.0077x10^-6	（25℃）
シュウ酸カルシウム	0.00257x10^-6	（25℃）
オレイン酸カルシウム	0.000291x10^-6	（25℃）
パルチミン酸カルシウム	0.000000161x10^-6	（23℃）

カルシウムの吸収(SP.744)

＋健康成人の1日あたりの食物Ca摂取0.6g
＋消化管分泌物と脱落上皮細胞のCa 0.6g
－吸収されるCa　　　　　　　　　 0.7g
－そのまま排泄　　　　　　　　　　0.5g
正味吸収されるCa 0.1g

カルシウムの吸収部位

十二指腸

カルシウム代謝の調節機構

副甲状腺ホルモン、1,25水酸化ビタミンD₃、コルチゾール、カルシトニン、酸塩基平衡異常

副甲状腺ホルモン

血中Ca上昇＋血中P低下を行う。

1. 破骨細胞に作用してCa,Pが血中へ。
2. 腎の遠位尿細管に作用してCa再吸収の亢進、近位尿細管でのP再吸収の抑制。
3. 近位尿細管に作用して酵素を活性化し、1,25水酸化ビタミンD3の産生亢進。

1,25(OH)2D3

血中Ca上昇＋血中P上昇

1. 空腸からのCaとPの吸収。
2. 骨形成促進。
3. 遠位尿細管でのＣａとPの再吸収促進。
4. 副甲状腺ホルモンの合成を抑制

尿細管における部位別カルシウム輸送

糸球体で濾過されるのはイオン化Caと陰イオン複合型Ca(蛋白結合型Caは濾過されない)
濾過されたカルシウムのうち95%が再吸収される。

近位尿細管：60-70%
ヘンレループ：20-25%
遠位尿細管、集合管：10-15%

近位尿細管

Na⁺依存的に再吸収。受動輸送80%、能動輸送20%

基底側のCa²⁺ ATPase, 3Na⁺-Ca²⁺逆輸送系

ヘンレループ

太いヘンレループ上行脚で
受動輸送：管腔内電位が正であるため

基底側の^Ca2+ ATPase

遠位尿細管～集合管

糸球体濾過量の10-15%が再吸収されている　→　量としては少ないが能動的に吸収が行われる部位。
能動輸送：管腔内電位が負であるため。
PTH、カルシトニンに調節されている

チアジド系利尿薬により細胞内Na↓となるとCa再吸収↑となる！！！！　←　ループ利尿薬と違う点。よって高カルシウム血症が起こることがある。

接合尿細管

管腔側：Ca2+チャネル/非選択的カチオンチャネル
基底側：Na+-K+ ATPase, 3Na+-Ca2+交換系

尿細管におけるカルシウムの輸送の調節 SP.796

循環血漿量

Ca2+の尿中排泄量はNa+の尿中排泄量と比例。循環血漿量が増加するとCa2+排泄も増加

血漿電解質濃度

Ca2+の尿中排泄量は血漿Ca2+濃度と比例する。

酸塩基平衡

Ca2+の尿中排泄量は代謝性アシドーシスで増加。遠位尿細管でのCa2+再吸収が抑制されるため。

血清カルシウム濃度

血液中でCa2+は調節を受けて一定に保たれるが、蛋白と結合しているCaはアルブミンの量によって増減する。

血清アルブミン濃度 4 g/dl、血清Ca濃度 9mg/dl。補正Ca濃度 9mg/dl　→　正常

血清アルブミン濃度 2 g/dl、血清Ca濃度 7mg/dl。　→　大変！！低カルシウム血症！！　→　ホント？　ってことになる。アルブミンの量が減ってAlb-Caが減っただけで生理的に重要なCa2+は保たれているのではないか。　→　こんな時に補正Ca濃度を用いるのである

　　　　　　　　　　　　　　　　　　　　　　　→補正Ca濃度 9mg/dl →　正常

つまり、低アルブミン血症ではCa2+は保たれているにもかかわらず、血清Caは低値となりそのままでは評価できないために補正を行う。

補正Ca濃度(mg/dl)＝Ca実測値(mg/dl)＋(4－血清アルブミン濃度(g/dl))　・・・Payneの式

アルブミンのpIは7より小さく、アシデミアでは負に帯電しているアルブミンが減少、アルカレミアでは負に帯電しているアルブミンが増加する。すなわち、pHが下がるとアルブミンとくっつなくなったCaが増加するので、血液pH0.1の低下につきfreeイオン化Ca(Ca2+)は0.12mg/dl増加する？？？？？？？？？？？

循環血液量

循環血液量↑→尿中Na排泄↑、尿中Ca排泄↑

血清Ca濃度

血清Ca濃度↑→PTH↓
生理活性のあるのはイオン化Ca(Ca²⁺)のみ

血清Ca濃度＝イオン化Ca(45%) + 蛋白結合型Ca(40%) + 陰イオン複合型Ca(15%)

イオン化Caは一定に保たれる

pH

Ca²⁺はアルブミンなどに結合しているがpI<7.4である。

アシドーシス　:pHが小さくなると負電荷減少：蛋白のCa結合能↓、イオン化Ca↑

アルカローシス:pHが大きくなると負電荷増加：蛋白Caの結合能↑、イオン化Ca↓→Ca欠乏(低カルシウム血症)

低蛋白血症

低蛋白血症の際、蛋白結合型Caは減少するが、イオン化Ca一定。

尿中カルシウム

リン負荷→(血中Ca2+↓)→尿中Ca2+排泄↓
リン制限→(血中Ca2+↑)→尿中Ca2+排泄↑
代謝性アシドーシス→尿中Ca2+排泄↑
PTH→尿中Ca2+排泄↓
カルシトニン→尿中Ca2+排泄↑
多くの利尿薬→(尿中Na+↑)→尿中Ca2+排泄↑　　(浸透圧利尿薬、ループ利尿薬) see 利尿薬
チアジド系利尿薬、炭酸脱水酵素阻害薬、アミロライド→尿中Ca2+排泄↓

血中カルシウムと尿中カルシウム

薬剤などの影響がなければ、血中カルシウムと尿中カルシウムは相関がありそうである　→　副甲状腺ホルモン

血清カルシウムと心電図

QT時間と血清カルシウムは負の相関関係にある

元素

金属元素。周期表第2族アルカリ土類金属元素
原子番号：20
元素記号：Ca
原子量 40.078 g/mol

臨床関連

骨粗鬆症

カルシウム剤：カルシウムの補充

参考

カルシウム製剤の特徴

http://www.orth.or.jp/osteoporose/caseizai.html

「100Cases 16」

　　[★]

☆case16　膝の痛み

■glossary

indigestion 消化障害、消化不良

■症例

80歳　男性

主訴：左膝の痛みと腫脹

現病歴：左膝の痛みを2日前から認めた。膝は発熱・腫脹しており、動かすと疼痛を生じる。時々胸焼けと消化不良が見られる。6ヶ月前のhealth checkで、高血圧(172/102mmHg)と血中クレアチニンが高い(正常高値)こと以外は正常といわれた。その4週間数回血圧を測定したが、高値が継続したため、2.5mg bendrofluamethizide(UK)/ベンドロフルメチアジド bendroflumethiazide(US)で治療を開始した。最近の血圧は138/84 mmHgであった。

喫煙歴：なし。

飲酒歴：一週間に平均4unit。

既往歴：股関節に中程度(mild)の変形性関節症

家族歴：特記なし

服薬歴：アセトアミノフェン(股関節の疼痛に対して)

身体所見 examination

　血圧 142/86mmHg。体温37.5℃。脈拍88/分。grade 2 hypertensive retinopathy(高血圧症性網膜症)。心血管系、呼吸器系に検査場異常なし。手にDIPにヘバーデン結節なし。

　左膝が発熱し腫脹している。関節内に液、patellar tap陽性。90℃以上膝関節を屈曲させると痛みを生じる。右の膝関節は正常に見える。

検査　 investigation

　生化学：白血球増多、ESR 上昇、尿素高値、グルコース高値

　単純X線：関節間隙やや狭小。それ以外に異常は認めない。

■problem list

　#1 左膝の痛み

　#2 胸焼け

　#3 消化不良

　#4 高血圧

　#5 クレアチニン正常高値

　#6 股関節の変形性リウマチ

　#7 高血圧性網膜症

■考え方

　・関節痛の鑑別診断を考える。

　・VINDICATEで考えてみてもよいでしょう。

　・関節痛の頻度としては　外傷＞慢性疾患(OAなど)＞膠原病＞脊椎疾患＞悪性腫瘍

■関節痛の鑑別疾患

DIF 282

V Vascular 血友病 hemophilia, 壊血病 scurvy, 無菌性骨壊死 aseptic bone necrosis (Osgood-Schlatter diseaseとか)

I Inflammatory 淋疾 gonorrhea, ライム病 lyme disease, 黄色ブドウ球菌 Staphylococcus, 連鎖球菌 Streptococcus, 結核 tuberculosis, 梅毒 syphilis, 風疹 rubella, 単純ヘルペス herpes simplex, HIV human immunodeficiency virus, サイトメガロウイルス cytomegalovirus

N Neoplastic disorders 骨原性肉腫 osteogenic sarcoma, 巨細胞腫 giant cell tumors

D Degenerative disorders degenerative joint disease or 変形性関節症 osteoarthritis

I Intoxication 痛風 gout (uric acid), 偽痛風 pseudogout (calcium pyrophosphate), ループス症候群 lupus syndrome of hydralazine (Apresoline) and procainamide, gout syndrome of diuretics

C Congenital and acquired malformations bring to mind the joint deformities of tabes dorsalis and syringomyelia and congenital dislocation of the hip. Alkaptonuria is also considered here.