|Classification and external resources|
Sheehan's syndrome, also known as Simmond's 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.
Signs and symptoms
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. In Sheehan's syndrome, one or more of these hormones cannot perform their jobs, so these problems result.
Most common initial symptoms of Sheehan's syndrome are agalactorrhea (absence of lactation) and/or difficulties with lactation. Many women also report amenorrhea or oligomenorrhea after delivery. In some cases, a woman with Sheehan's syndrome might be relatively asymptomatic, and the diagnosis is not made until years later, with features of hypopituitarism. 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. The symptoms of adrenal crisis should be treated immediately and can be life-threatening  Gonadotropin deficiency will often cause amenorrhea, oligomenorrhea, hot flashes, or decreased libido. Growth hormone deficiency causes many vague symptoms including fatigue and decreased muscle mass.
Uncommonly, Sheehan's syndrome may also appear acutely after delivery, mainly by hyponatremia. Hypopituitarism can result in hyponatremia by several possible mechanisms, 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). The potassium level in these situations is normal, because adrenal production of aldosterone is not dependent on the pituitary. There have also been cases with acute hypoglycemia, presumably from lack of cortisol.
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. 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.
In a study of 1,034 symptomatic adults, Sheehan's 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).
The specific association with postpartum shock or haemorrhage was described in 1937 by the British pathologist Harold Leeming Sheehan (1900–1988), whereas Simmond's disease occurs in either sex due to causes unrelated to pregnancy.
- First Aid for the Obstetrics and Gynecology Clerkship, p. 226, PITUITARY (HYPOESTROGENIC AMENORRHEA)
- Schrager S, Sabo L (2001). "Sheehan syndrome: a rare complication of postpartum hemorrhage". J Am Board Fam Pract. 14 (5): 389–91. PMID 11572546.
- Bunch TJ, Dunn WF, Basu A, Gosman RI (October 2002). "Hyponatremia and hypoglycemia in acute Sheehan's syndrome". Gynecol. Endocrinol. 16 (5): 419–23. doi:10.1080/gye.16.5.419.423. PMID 12587538.
- Rabkin MT & Frantz AG. Hypopituitarism: a study of growth hormone and other endocrine functions. Annals of Internal Medicine 1966 64 1197–1207.
- Kelestimur F, Jonsson P, Molvalilar S, Gomez JM, Auernhammer CJ, Colak R, Koltowska-Häggström M, Goth MI. Sheehan's syndrome: baseline characteristics and effect of 2 years of growth hormone replacement therapy in 91 patients in KIMS - Pfizer International Metabolic Database. Eur J Endocrinol. 2005 Apr;152(4):581-7.
- http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=endocrin&part=A1257 under heading Sheehan's syndrome
- Keleştimur F. GH deficiency and the degree of hypopituitarism. Clinical Endocrinology 1995 42 443–444.
- Abs, R; Bengtsson, BA; Hernberg-Stâhl, E; Monson, JP; Tauber, JP; Wilton, P; Wüster, C (June 1999). "GH replacement in 1034 growth hormone deficient hypopituitary adults: demographic and clinical characteristics, dosing and safety.". Clinical endocrinology. 50 (6): 703–13. PMID 10468941.
- H. L. Sheehan. Post-partum necrosis of anterior pituitary. The Journal of Pathology and Bacteriology, Chichester, 1937, 45: 189-214.
- Sheehan's syndrome at Who Named It?