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Difficulty: MediumMenstrual Cycle Abnormalities and Contraception

A 3131-year-old woman comes to the clinic for evaluation of amenorrhea. She has not had a menstrual period since the vaginal delivery of her first child 1414 months ago. Her pregnancy was complicated by placental abruption and severe postpartum hemorrhage that required emergency fluid resuscitation and a blood transfusion. The patient reports she was never able to produce breast milk despite multiple attempts to breastfeed. Over the past six months, she has also noted significant fatigue, a 1010-lb (4.54.5-kg) weight loss, and feeling cold all the time. On physical examination, blood pressure is 90/6090/60 mmHg and pulse is 5858/min. She has dry skin, sparse pubic hair, and delayed relaxation of deep tendon reflexes. A urine pregnancy test is negative.

Which of the following sets of laboratory test results is most likely in this patient?

  1. Decreased free T4, decreased TSH, decreased prolactin, and decreased FSHAnswer
  2. B
    Decreased free T4, increased TSH, increased prolactin, and decreased FSH
  3. C
    Decreased free T4, decreased TSH, increased prolactin, and decreased FSH
  4. D
    Normal free T4, normal TSH, normal prolactin, and an increased LH-to-FSH ratio
  5. E
    Normal free T4, normal TSH, normal prolactin, and increased FSH

Answer

The correct laboratory pattern is decreased free T4, decreased TSH, decreased prolactin, and decreased FSH.
The correct answer demonstrates a global decrease in anterior pituitary hormones. This patient's presentation of secondary amenorrhea, failure to lactate, and symptoms of hypothyroidism following a complicated delivery with severe postpartum hemorrhage is highly characteristic of Sheehan syndrome (postpartum pituitary gland necrosis). During pregnancy, the anterior pituitary gland enlarges and becomes highly vascular, making it vulnerable to ischemic necrosis in the setting of severe hypotension or hypovolemic shock (e.g., severe postpartum hemorrhage). Ischemic necrosis leads to panhypopituitarism. Loss of prolactin results in failure of lactation, which is often the earliest clinical symptom. Loss of gonadotropins (FSH and LH) leads to secondary amenorrhea. Loss of thyroid-stimulating hormone (TSH) leads to secondary hypothyroidism (evidenced by decreased free T4, fatigue, cold intolerance, bradycardia, and delayed deep tendon reflexes). Loss of adrenocorticotropic hormone (ACTH) leads to secondary adrenal insufficiency, presenting with weight loss, hypotension, and sparse pubic hair (due to decreased adrenal androgens). Therefore, laboratory testing would show a decrease in anterior pituitary hormones (TSH, prolactin, FSH) and their downstream target hormones (such as free T4).

Step-by-Step Solution

1
Identify the primary presentation and relevant obstetric history.
The patient presents with secondary amenorrhea and failure of lactation following a severe postpartum hemorrhage.
Recognizing the connection between postpartum hemorrhage and subsequent amenorrhea is key to identifying the underlying etiology.
2
Evaluate the associated systemic symptoms and physical examination findings.
The patient exhibits signs of hypothyroidism (fatigue, cold intolerance, bradycardia, delayed reflexes) and adrenal insufficiency (hypotension, weight loss, sparse pubic hair).
Systemic signs point to a generalized endocrine dysfunction rather than an isolated reproductive axis abnormality.
3
Synthesize the findings to determine the most likely diagnosis.
The combination of multiple anterior pituitary hormone deficiencies following obstetric hemorrhage indicates panhypopituitarism due to Sheehan syndrome.
Sheehan syndrome occurs due to ischemic necrosis of the enlarged pituitary gland during hypovolemic shock, leading to deficiency of all anterior pituitary hormones.
4
Predict the corresponding laboratory findings based on the diagnosis.
Because the anterior pituitary is infarcted, stimulating hormones (TSH, FSH, LH, ACTH, prolactin) and their downstream targets (free T4) will all be decreased.
A destructive pituitary lesion abolishes the entire hypothalamic-pituitary-end organ axis.

Key Concept

Sheehan syndrome (postpartum pituitary necrosis) presents with panhypopituitarism, causing secondary amenorrhea, failure to lactate, and secondary hypothyroidism/adrenal insufficiency due to global anterior pituitary hormone deficiency.
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Topics

Menstrual Cycle Abnormalities and Contraception

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