出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/08/13 09:05:06」(JST)
| Sheehan syndrome | |
|---|---|
| Classification and external resources | |
| Specialty | endocrinology |
| ICD-10 | E23.0 |
| ICD-9-CM | 253.2 |
| DiseasesDB | 11998 |
| MedlinePlus | 001175 |
| eMedicine | med/1914 |
| MeSH | D007018 |
Sheehan syndrome, also known as Simmond syndrome, postpartum hypopituitarism or postpartum pituitary gland necrosis, is hypopituitarism (decreased functioning of the pituitary gland), caused by ischemic necrosis due to blood loss and hypovolemic shock during and after childbirth.[1]
The various signs and symptoms in Sheehan's syndrome are caused by damage to the pituitary, which causes a decrease in one or more hormones it normally secretes (see Pathophysiology section). In Sheehan's syndrome, one or more of these hormones cannot perform their jobs, so the following problems result.
Most common initial symptoms of Sheehan's syndrome are agalactorrhea (absence of lactation) and/or difficulties with lactation.[2] Many women also report amenorrhea or oligomenorrhea after delivery.[2] In some cases, a woman with Sheehan syndrome might be relatively asymptomatic, and the diagnosis is not made until years later, with features of hypopituitarism.[2] Such features include secondary hypothyroidism with tiredness, intolerance to cold, constipation, weight gain, hair loss and slowed thinking, as well as a slowed heart rate and low blood pressure. Another such feature is secondary adrenal insufficiency, which, in the rather chronic case is similar to Addison's disease with symptoms including fatigue, weight loss, hypoglycemia (low blood sugar levels), anemia and hyponatremia (low sodium levels). Such a woman may, however, become acutely exacerbated when her body is stressed by, for example, a severe infection or surgery years after her delivery, a condition equivalent with an Addisonian crisis.[2] The symptoms of adrenal crisis should be treated immediately and can be life-threatening [3] Gonadotropin deficiency will often cause amenorrhea, oligomenorrhea, hot flushes, or decreased libido.[2] Growth hormone deficiency causes many vague symptoms including fatigue and decreased muscle mass.[2]
Uncommonly, Sheehan syndrome may also appear acutely after delivery, mainly by hyponatremia.[2] There are several possible mechanisms by which hypopituitarism can result in hyponatremia, including decreased free-water clearance by hypothyroidism, direct syndrome of inappropriate antidiuretic hormone (ADH) hypersecretion, decreased free-water clearance by glucocorticoid deficiency (independent of ADH).[2] The potassium level in these situations is normal, because adrenal production of aldosterone is not dependent on the pituitary.[2] There have also been cases with acute hypoglycemia, presumably from lack of cortisol.[4]
The order of frequency of hormone loss has generally been found to be growth hormone, gonadotropins (FSH, LH), adrenocorticotrophin (ACTH) and thyroid stimulating hormone (TSH).[5][6]
It is a rare complication of pregnancy, usually occurring after excessive blood loss. The presence of disseminated intravascular coagulation (i.e., in amniotic fluid embolism or HELLP syndrome) also appears to be a factor in its development.
Hypertrophy and hyperplasia of lactotrophs during pregnancy results in the enlargement of the anterior pituitary, without a corresponding increase in blood supply.
Secondly, the anterior pituitary is supplied by a low pressure portal venous system.[7]
These vulnerabilities, when affected by major hemorrhage or hypotension during the peripartum period, can result in ischaemia of the affected pituitary regions leading to necrosis.
The posterior pituitary is usually not affected due to its direct arterial supply.
A 1995 study found that 56.2% of patients with Sheehan’s syndrome experienced a loss of all pituitary hormones (with the remaining 43.8% having selective pituitary insufficiency). However, likely because the growth hormone-secreting cells are located at the periphery of the pituitary (and are therefore most likely to be affected by ischemia), all the patients had growth hormone deficiency.[8]
The pathophysiology of signs and symptoms in Sheehan's syndrome is explained by a decrease in circulation of one or more hormones, since the pituitary is damaged and loses the cells that normally secrete them. Highly relevant hormones include prolactin (normally stimulates lactation, and lowers dopamine levels), ADH (stimulates kidneys to reabsorb water so you do not get dehydrated), TSH (stimulates the thyroid), and cortisol (allows the body to survive in times of severe physical stress, such as when one is sick, and helps other hormones keep blood sugar levels elevated). Without these hormones, their respective jobs are not performed, and the signs and symptoms of pituitary damage ensue, in this case from Sheehan's syndrome. To note, it is because so many unique problems may result that this is known as a "syndrome".
In a study of 1,034 symptomatic adults, Sheehan syndrome was found to be the sixth most frequent etiology of growth hormone deficiency, being responsible for 3.1% of cases (versus 53.9% due to a pituitary tumor).[9]
The specific association with postpartum shock or haemorrhage was described in 1937 by the British pathologist Harold Leeming Sheehan (1900–1988),[10] whereas Simmond's disease occurs in either sex due to causes unrelated to pregnancy.[11]
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| リンク元 | 「シーハン症候群」「pituitary insufficiency」 |
| 関連記事 | 「syndrome」 |
| ACTH↓ | 易疲労感、低血糖、低ナトリウム血症、低血圧、恥毛・腋毛の脱落 | |
| PRL↓ | 乳汁分泌低下 | |
| TSH↓ | 耐寒性の低下、不活発、便秘、皮膚の乾燥 | |
| GH↓ | 筋力低下、体脂肪増加 | |
| FSH・LH↓ | エストロゲン↓ | 第2度無月経、性欲低下、乳房・内外性器の萎縮、骨粗鬆症 |
| プロゲステロン↓ | 基礎体温：低温1相 | |