Sheehan's syndrome, also known as postpartum pituitary gland necrosis, occurs when the pituitary gland is damaged due to significant blood loss and hypovolemic shock (ischemic necrosis) or stroke, originally described during or after childbirth leading to decreased functioning of the pituitary gland (hypopituitarism). Classically, in the milder partial form, the mother is unable to breastfeed her baby, due to failure of the pituitary to secrete the hormone prolactin, and also has no more periods, because FSH (Follicle Stimulating Hormone) and LH (Luteinising Hormone) are not secreted. Although postmenopausal, the mother with this milder form of Sheehan's syndrome does not experience hot flushes, because the pituitary fails to secrete FSH (high levels of FSH, secreted by the pituitary in healthy postmenopausal women is an attempt to trigger ovulation, and these high levels of FSH cause the hot flushes).
The failure to breastfeed and amenorrhea were seen as the syndrome (a collection of symptoms), but we now view Sheehan's as the pituitary failing to secrete 1-5 of the 9 hormones that it normally produces (the anterior (front) lobe of the pituitary produces FSH, LH, prolactin, ACTH (Adreno-cortico-trophic hormone),TSH (Thyroid Stimulating Hormone) and GH (Growth Hormone); the posterior (the lobe at the back) pituitary produces ADH (Anti-Diuretic Hormone) and Oxytocin, i.e. the pituitary is involved in the regulation of many hormones. It is very important to recognise Sheehan' stroke as, the ACTH deficiency Sheehan's in the presence of the stress of a bacterial infection, such as a urine infection, will result in death of the mother from Addisonian crisis. This gland is located on the under-surface of the brain, the shape of a cherry and the size of a chickpea and sits in a pit or depression of the sphenoid bone known as the sella turcica (the Turk's saddle).
The pituitary gland works in conjunction with the hypothalamus, and other endocrine organs to modulate numerous bodily functions including growth, metabolism, menstruation, lactation, and even the "fight-or-flight" response. Many of the signs and symptoms of Sheehan's are considered "nonspecific" in the medical community; in other words these signs and symptoms are seen in a number of different disease processes, and are not specific to a singular disease or syndrome.
In some cases, a woman with Sheehan syndrome may be relatively asymptomatic initially; therefore, the diagnosis would not be made until years later when features of hypopituitarism become evident. In rare instances this syndrome can present acutely with unstable vital signs, dangerously low blood glucose levels, heart failure, or even psychosis. In addition to menstrual irregularities other signs of sex hormone deficiency are hot flashes, decreased libido, and breast involution. Adrenal gland malfunction can present acutely or chronically. In a more chronic case, it is similar to Addison's disease with symptoms including fatigue, weight loss, hypoglycemia (low blood sugar levels), low hemoglobin levels (anemia) and hyponatremia (low sodium levels) that develop over several months or years. Acute adrenal insufficiency is referred to as an adrenal crisis, which can be life-threatening, and occurs very shortly after the inciting event i.e. significant blood loss post-partum in the context of Sheehan's syndrome. Adrenal crisis signs and symptoms include hypoglycemia, hypotension, weakness, fatigue, and seizures from severe hyponatremia. Hematological changes might be seen as well such as anemia or low platelets (thrombocytopenia).
Pathophysiology
This syndrome seems to arise when certain factors compound each other to cause pituitary injury. The physiologic enlargement of the pituitary gland in conjunction with an interference in its blood supply, such as episiotomy progressing to anal tearing, ultimately result in pituitary ischemia and necrosis. Later in the disease process of this syndrome the damage imposed on the pituitary gland will cause it to shrink, and leave a partially empty or totally empty sella turcica on MRI. Treatment plans and dosages should be individualized by an endocrinologist. Glucocorticoids may be administered to address or prevent an adrenal crisis, a potential serious complication of Sheehan's syndrome. The initial distinction was made in the research article "Post-Partum Necrosis of the Anterior Pituitary". In his research, Dr. Sheehan reviewed (through autopsy) the effects of pituitary necrosis on 12 cases of patients that experienced postpartum necrosis. According to Sheehan in 1939 approximately 41% of survivors of severe postpartum hemorrhage (PPH) and/or hypovolemic shock experienced severe or partial hypopituitarism. Given that many patients that have developed Sheehan's syndrome do not have detectable levels of these antibodies, it is unclear whether these antibodies cause this syndrome or result from it.