Sheehan’s syndrome, also known as postpartum pituitary gland necrosis, is hypopituitarism caused by ischemic necrosis due to blood loss and hypovolemic shock during and after childbirth.
Signs and symptoms in Sheehan’s syndrome are caused by damage to the pituitary, causing a decrease in one or more of the hormones it normally secretes.
The anterior pituitary is supplied by a low pressure portal venous system.
Partial or complete loss of a variety of functions may result.
More than half of patients with diagnosed Sheehan’S syndrome experienced a loss of all pituitary hormones.
The remaining patients having selective pituitary insufficiency.
Since the growth hormone-secreting cells are located at the periphery of the pituitary and are most likely affected by ischemia, all of the patients experience growth hormone deficiency.
The most common initial symptom of Sheehan’s syndrome is the absence of lactation and/or difficulties with lactation.
Some women with Sheehan syndrome are relatively asymptomatic.
In such women the diagnosis would not be made until years later, with other features of hypopituitarism:
secondary hypothyroidism, secondary adrenal insufficiency.
Gonadotropin deficiency will often cause amenorrhea, oligomenorrhea, hot flashes, decreased libido or cessation of menses.
Growth hormone deficiency causes
fatigue and decreased muscle mass.
Growth-hormone deficiency is the most common symptom of hypopituitarism seen in Sheehan’s syndrome.
Hematological changes due to a decrease in erythropoietin synthesis as a result of these cortisol and thyroid hormone decreases.
Sheehan syndrome may also appear acutely after delivery, and is associated with hyponatremia.
Electrolytic imbalances might result from the increased secretion of ADH, caused by a decrease in blood pressure due to lower glucocorticoid deficiency.
Mechanisms for hypopituitarism can result in hyponatremia: decreased free-water clearance by hypothyroidism, direct syndrome of inappropriate antidiuretic hormone (ADH) hypersecretion, decreased free-water clearance by glucocorticoid deficiency (independent of ADH).
Serum potassium levels, do not change due to Sheehan’s syndrome: potassium levels are primarily regulated
by the renin-angiotensin-aldosterone system.
It is a rare complication of pregnancy, usually manifesting after excessive blood loss after delivery.
The presence of disseminated intravascular coagulation also appears to be a factor in its development.
Pituitary necrosis may be a direct result from a lack of blood flow in the hypophyseal artery as a result of pituitary gland enlargement during pregnancy.
Hyperplasia of lactotrophs that are responsible for prolactin production is one cause of pituitary growth associated with the risk of Sheehan’s syndrome.
Pituitary ischemia may be a result of vasospasm, thrombosis, or vascular compression sometimes as a result of an increase in the amount of lactotroph cells throughout gestation.
Necrosis may result from severe hypotension or shock due to excessive uterine bleeding following childbirth.
It may occur from arterial constriction and abnormal hypotension in conjunction with an insufficiency to meet the increased demand in blood supply of the pituitary gland seen during pregnancy.
Possible predisposing factors:
inherited or acquired disseminated blood coagulation (DIC), restriction in pituitary blood supply, small sella size, vasospasm, or thrombosis, anaemia, obesity, and advanced maternal age may increase the risk of Sheehan Syndrome.
Atony of the uterus may be related to postpartum bleeding that could induce Sheehan’s syndrome.
Laboratory evaluation include hormonal assays to determine levels of T4, TSH, estrogen, gonadotropin, cortisol, and ACTH depending on the extent of necrosis.
If hormone levels are borderline, stimulation tests will be done to determine if the pituitary is responsive to hypothalamic hormones.
Treatment: Lifelong hormone replacement therapy for the hormones that are missing.
Sheehan’s syndrome was found to be the sixth-most frequent etiology of growth hormone deficiency, being responsible for 3.1% of cases.
It is more prevalent in developing countries, and the majority of women who experience Sheehan syndrome give birth at home.