Sheehan's Syndrome and Hypopituitarism

The correct answer is E.

Sheehan's syndrome is hypopituitarism due to ischemic damage to the pituitary resulting from excessive hemorrhage during parturition. The pituitary is enlarged during pregnancy; it is more metabolically active, and more susceptible to hypoxemia. Furthermore, the blood vessels in the pituitary may be more susceptible to vasospasm because of the high estrogen. In about 30% of women who hemorrhage excessively during parturition, some degree of hypopituitarism eventually becomes manifest. The symptoms depend on how much of the pituitary is damaged and what cell types are destroyed. The patient described above exhibited persistent amenorrhea after delivery of her infant. This is due to destruction of pituitary gonadotrophs and diminished secretion of gonadotropins (LH). There also appears to have been significant destruction of lactotrophs since TRH injection failed to induce an increase in prolactin. Had the women attempted to breast-feed her infant, a failure to lactate mostly likely would have occurred. This case is also characterized by secondary hypothyroidism. The low TSH and failure to respond to TRH injection is confirmatory. Corticotrophs appear to have been spared since plasma ACTH is normal. It is not clear whether somatotrophs were damaged. Further testing would be needed to see if GH reserve is diminished.

Hashimoto's thyroiditis (choice A) is an autoimmune disorder that produces primary hypothyroidism. Because of diminished negative feedback effects of T4, serum TSH is usually increased (not decreased).

Isolated gonadotropin deficiency (choice B) produces amenorrhea and is associated with low serum LH and estradiol. Hypogonadotropic hypogonadism can occur in female athletes that over-train, in anorexia nervosa, in obesity, or with other emotional or physical stresses. However, other pituitary hormones are unaffected (by definition isolated gonadotropin deficiency only involves a decrease in gonadotropins).

Primary amenorrhea (choice C), by definition, means failure of menstrual cycles to ever begin. Since this woman has delivered a baby, primary amenorrhea is highly unlikely.

A prolactinoma (choice D) is a functional pituitary tumor that secretes excessive prolactin. This can cause amenorrhea by suppressing the GnRH-pituitary-gonad axis. The patient described above has decreased prolactin secretion.