シーハン症候群

Sheehan syndrome or postpartum hypopituitarism is a condition characterized by hypopituitarism due to necrosis of the pituitary gland. The initial insult is caused by massive postpartum haemorrhage (PPH), leading to impaired blood supply to the pituitary gland, which has become enlarged during pregnancy. Small sella turcica size, vasospasms (caused by PPH) and/or thrombosis (associated with pregnancy or coagulation disorders) are predisposing factors; autoimmunity might be involved in the progressive worsening of pituitary functions. Symptoms are caused by a decrease or absence of one or more of the pituitary hormones, and vary, among others, from failure to lactate and nonspecific symptoms (such as fatigue) to severe adrenal crisis. In accordance with the location of hormone-secreting cells relative to the vasculature, the secretion of growth hormone and prolactin is most commonly affected, followed by follicle-stimulating hormone and luteinizing hormone; severe necrosis of the pituitary gland also affects the secretion of thyroid-stimulating hormone and adrenocorticotropic hormone. Symptoms usually become evident years after delivery, but can, in rare cases, develop acutely. The incidence of Sheehan syndrome depends, to a large extent, on the occurrence and management of PPH. Sheehan syndrome is an important cause of hypopituitarism in developing countries, but has become rare in developed countries. Diagnosis is based on clinical manifestations combined with a history of severe PPH; hormone levels and/or stimulation tests can confirm clinical suspicion. Hormone replacement therapy is the only available management option so far.