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 are secreted by the pituitary in healthy postmenopausal women in an attempt to trigger ovulation; these high levels of FSH cause the hot flushes). The syndrome used to be seen as a failure to breastfeed plus amenorrhea (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 pituitary (the lobe at the back) produces ADH (anti-diuretic hormone) and oxytocin. In other words, the pituitary is involved in the regulation of many hormones. It is very important to recognise Sheehan's 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. These endocrine organs, (like the thyroid gland in the neck, or adrenals on the upper pole of the kidneys), release hormones in very specific pathways, known as hormonal axes. For example, the release of a hormone in the hypothalamus will target the pituitary to trigger the release thyroid stimulating hormone (TSH), and the pituitary's released hormone (TSH) will target the next organ in the pathway i.e. the thyroid to release thyroxin. Hence, damage to the pituitary gland can have downstream effects on any of the aforementioned bodily functions.
Signs and symptoms The various signs and symptoms in Sheehan's syndrome are caused by damage to the pituitary, thereby causing a decrease in one or more of the hormones it normally secretes. Since the pituitary controls many glands in the endocrine system, partial or complete loss of a variety of functions may result. 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. Hypopituitarism can lead to an interruption in any of the following hormone pathways: thyroid disorder (secondary hypothyroidism), adrenal gland (adrenal insufficiency due to glucocorticoid deficiency), sex hormone (gonadotropin deficiency), prolactin (a hormone responsible for lactation), growth hormone, or rarely anti-diuretic hormone deficiency (central diabetes insipidus). Since damage to the pituitary can cause a deficiency in more than one of these hormone pathways simultaneously, it is possible to have a mix of any of the signs or symptoms listed below. Sheehan's syndrome's most common initial symptoms are difficulties with or total absence of lactation (agalactorrhea). Another common sign is infrequent menstrual cycles (oligomenorrhea) or absent menstrual cycles (amenorrhea) following delivery. In addition to menstrual irregularities other signs of sex hormone deficiency are hot flashes, decreased libido, and breast involution. Symptoms and signs of thyroid disorder are tiredness, intolerance to cold, constipation, weight gain, hair loss, slowed thinking, as well as a slowed heart rate and low blood pressure. 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. Growth hormone deficiency is one of the most common hormone deficiencies of hypopituitarism seen in Sheehan's syndrome. Low levels of growth hormone may present with low energy, body aches, or subtle wrinkling of the skin around the eyes or mouth. The symptoms of anti-diuretic hormone deficiency are increased thirst, excessive urination, headache, and fatigue. Hematological changes might be seen as well such as anemia or low platelets (thrombocytopenia). Hyponatremia is seen in many cases of Sheehan's syndrome because it can result from multiple etiologies. Drops in thyroid hormones and glucocorticoid/adrenal hormones can indirectly lead to hyponatremia through water retention, while blood loss can trigger hyponatremia through ADH secretion. The development of Syndrome of Inappropriate Anti-Diuretic Hormone in patients with Sheehan's syndrome has been documented in the literature, although the mechanism is not well understood.
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