出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/06/05 00:23:45」(JST)
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| False pregnancy | |
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| Classification and external resources | |
| Specialty | Psychiatry |
| ICD-10 | F45.8 |
| ICD-9-CM | 300.11 |
| DiseasesDB | 29264 |
| MeSH | D011555 |
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[edit on Wikidata]
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False pregnancy, phantom pregnancy, or hysterical pregnancy— officially called pseudocyesis in humans and pseudopregnancy in other mammals—is the appearance of clinical or subclinical signs and symptoms associated with pregnancy when the organism is not actually pregnant. Clinically, false pregnancy is most common in veterinary medicine (particularly in dogs and mice). False pregnancy in humans is less common, and may sometimes be purely psychological. It is generally believed that false pregnancy is caused by changes in the endocrine system of the body, leading to the secretion of hormones that cause physical changes similar to those during pregnancy. Some men experience the same illnesses as a woman would experience while pregnant when their partner is pregnant (see Couvade syndrome), possibly caused by pheromones that increase estrogen, prolactin, and cortisol levels.
The symptoms of pseudocyesis are similar to the symptoms of true pregnancy and are often hard to distinguish from it. Such natural signs as amenorrhoea, morning sickness, tender breasts, and weight gain may all be present. Many health care professionals can be deceived by the symptoms associated with pseudocyesis. Research shows that 18% of women with pseudocyesis were at one time diagnosed as pregnant by medical professionals.[citation needed]
The hallmark sign of pseudocyesis that is common to all cases is that the affected patient is convinced that she is pregnant. Abdominal distension is the most common physical symptom of pseudocyesis (60–90%). The abdomen expands in the same manner as it does during pregnancy, so that the affected woman looks pregnant. These symptoms often resolve under general anesthesia and the woman's abdomen returns to its normal size.[1]
The second most common physical sign of pseudocyesis is menstrual irregularity (50–90%). Women are also reported to experience the sensation of fetal movements known as quickening, even though there is no fetus present (50–75%). Other common signs and symptoms include gastrointestinal symptoms, breast changes or secretions, labor pains, uterine enlargement, and softening of the cervix. One percent of women eventually experience false labor.[citation needed]
To be diagnosed as true pseudocyesis, the woman must actually believe that she is pregnant. When a woman intentionally and consciously feigns pregnancy, it is termed a simulated pregnancy.
Symptoms of pseudocyesis can also occur in men who have couvade syndrome.[citation needed]
There are various explanations, none of which is universally accepted because of the complex involvement of cortical, hypothalamic, endocrine, and psychogenic factors.[2] Proposed mechanisms include the effect of stress on the hypothalamo-pituitary-adrenal axis, constipation, weight gain, and the movement of intestinal gas.
Pseudocyesis is not known to have a direct underlying physical cause and there are no general recommendations regarding treatment with medications. In some cases, however, the patient may be given medications for such symptoms as the cessation of menstruation. When some patients with pseudocyesis have underlying psychological problems, they should be referred to a psychotherapist for the treatment of these problems. It is important at the same time, however, for the treating professional not to minimize the reality of the patient's physical symptoms. The treatment that has had the most success is demonstrating to the patient that she is not really pregnant by the use of ultrasound or other imaging techniques.
The rate of pseudocyesis in the United States has declined significantly in the past century. In the 1940s there was one occurrence for approximately every 250 pregnancies. This rate has since dropped to between one and six occurrences for every 22,000 births.[3] The average age of the affected woman is 33, though cases have been reported for girls as young as 6 and women as old as 79. More than two-thirds of women who experience pseudocyesis are married, and about one-third have been pregnant at least once.[citation needed]
Cases of pseudocyesis have been documented since antiquity. Hippocrates gave the first written account around 300 BC when he recorded 12 cases of women with the disorder. Mary I (1516–1558), Queen of England, was suspected to have had two phantom pregnancies, but this is strongly disputed; some historians believe that the queen's physicians mistook fibroid tumors in her uterus for a pregnancy, while others suspect either a molar pregnancy (proceeding to choriocarcinoma) or ovarian cancer was to blame. John Mason Good coined the term pseudocyesis from the Greek words pseudes (false) and kyesis (pregnancy) in 1923.
The corpus luteum (the remains of an ovulated ovarian follicle) is responsible for the development of maternal behavior and lactation, which are mediated by the continued production of progesterone by the corpus luteum through some or all of pregnancy. In most species the corpus luteum is degraded in the absence of a pregnancy. However, in some species, the corpus luteum may persist in the absence of pregnancy and cause "pseudopregnancy", in which the female will exhibit clinical signs of pregnancy.[4]
Dogs become pseudopregnant following an estrus phase in which the female dog is not bred, or in which she is bred by an infertile male. Most species require signals from an embryo (such as IFN-τ in ruminants) to alert the female's body of a pregnancy. This maternal recognition of pregnancy will cause persistence of the corpus luteum and the development of characteristics and behaviors necessary to care for offspring. Limited research suggests that progesterone secretion is similar in pregnant and non-pregnant female dog, so veterinary researchers hypothesize that they may not require molecular factors from the embryo for maternal recognition of pregnancy, and instead the corpus luteum persists regardless of pregnancy. Since the corpus luteum is not degraded, it will cause the development of maternal characteristics in the absence of pregnancy. Pseudopregnant dogs will develop their mammary glands, lactate, and build nests to varying degrees depending on breed. Although female dogs usually only cycle once or twice per year, pseudopregnancy is common.[5]
Cats become pseudopregnant following an estrus in which the queen is bred by an infertile male. Queens are induced ovulators, meaning that they will only ovulate and produce a corpus luteum if they are bred. As in dogs, the corpus luteum persists as if the queen were pregnant, because the queen's body cannot distinguish between the pregnant and non-pregnant state (aside from the initial mechanical trigger of coitus). Pseudopregnant queens rarely show any mammary enlargement or behavioural signs and therefore rarely require treatment. Pseudopregnancy in cats is uncommon as the queen must be bred by an infertile male to become pseudopregnant, compounded by the fact that cats are seasonal breeders.[6]
Mice become pseudopregnant following an estrus in which the female is bred by an infertile male, resulting in "sterile mating".[7] Like dogs, mice are spontaneous ovulators. However, they will not become pseudopregnant following an estrus in which the female is not bred because the corpus luteum will degrade rapidly in the absence of coitus. When the female is bred by an infertile male, the corpus luteum persists without an embryo, leading to pseudopregnancy. The female will develop mammary glands, lactate, and build nests in the pseudopregnant state. Pseudopregnancy in mice is somewhat common in laboratory mice because it is often induced for the purpose of implanting embryos into a surrogate dam, but is uncommon in wild mice because most wild males are fertile and will genuinely impregnate the female.[4]
Mycotoxins have been shown to be detrimental to sows and gilts by causing the female to retain a corpora lutea inhibiting cyclicity and causing a pseudopregnancy; as well as constant exhibition of estrus, and infertility. Pregnant females produce litters that result in a higher number of stillborns, mummified fetuses, and abortions. Prior to breeding, ingesting mycotoxins mimics the action of estradiol-17β. Specifically, Zearonol is able to bind to tissues that contain estrogenic receptors that would normally bind to estrogen causing the female to exhibit constant estrus. Boars are also affected by ingestion of mycotoxins. Testis of the boar has been shown to undergo a reduction of size by 30%. This is due to a smaller than normal size of the epididymis and vesicular cords. However, testosterone production is not affected.[8]
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| リンク元 | 「想像妊娠」 |
| 関連記事 | 「spurious」 |