This week, we are sharing another USMLE® Step 1-style practice question to test your knowledge of medical topics. Today’s case involves a 34-year-old woman with an inability to breastfeed her baby. Can you figure it out?
A 34-year-old woman, gravida 1 para 1, comes to the clinic due to an inability to breastfeed her baby. She had a spontaneous vaginal delivery of a healthy newborn at full-term 3 weeks ago. The labor was complicated by postpartum hemorrhage secondary to retained products of conception, and she required transfusion with 3 units of packed red blood cells. She has been using formula for feeding, as her milk never “came in.” Review of systems is significant for increased fatigue over the same period, which she attributes to lack of sleep. Temperature is 36.5°C (97°7 F), pulse is 102/min, and blood pressure is 92/76 mm Hg. Physical examination reveals cool, dry skin. Which of the following is the most likely cause of this patient’s condition?
A. Infarction of the hypothalamus
B. Lymphocytic infiltration of the thyroid gland
C. Lymphocytic infiltration of the pituitary gland
D. Necrosis of the anterior pituitary gland
E. Proliferation of lactotroph cells
F. Postpartum thyroiditis
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The correct answer to today’s USMLE® Step 1 Question is…
D. Necrosis of the anterior pituitary gland
Before we get to the Main Explanation, let’s look at the incorrect answer explanations. Skip to the bottom if you want to see the correct answer right away!
Incorrect answer explanations
The incorrect answers to today’s USMLE® Step 1 Question are…
A. Infarction of the hypothalamus
Incorrect: Infarction of the hypothalamus is a possible cause of hypopituitarism. However, it is rare, as postpartum hemorrhage commonly affects the hyperplastic pituitary gland.
B. Lymphocytic infiltration of the thyroid gland
Incorrect: The characteristic histopathological finding in Hashimoto thyroiditis is profuse lymphocytic infiltration of the thyroid, along with destruction of thyroid follicles. While these patients may also present with signs of hypothyroidism (e.g., fatigue, cool dry skin), this diagnosis does not adequately explain this patient’s inability to lactate and abnormal vitals.
C. Lymphocytic infiltration of the pituitary gland
Incorrect: Lymphocytic hypophysitis is characterized by lymphocytic infiltration and destruction of pituitary cells. Although this may also present as hypopituitarism during late pregnancy or the postpartum period, this patient’s postpartum hemorrhage followed by panhypopituitarism is suggestive of a different diagnosis.
E. Proliferation of lactotroph cells
Incorrect: Lactotrophs are cells in the anterior pituitary gland which produce prolactin. Proliferation of these cells results in prolactinoma, and its growth can cause compression of nearby cells, resulting in decreased secretion of other anterior pituitary hormones. This diagnosis is an unlikely cause of this patient’s condition, who is presenting with failure of lactation.
F. Postpartum thyroiditis
Incorrect: Postpartum thyroiditis is an autoimmune-mediated destructive thyroiditis within 1 year of parturition that results in the classic signs and symptoms of hypothyroidism (e.g., fatigue, constipation, cold intolerance). Although this patient is presenting with signs and symptoms of hypothyroidism, she has additional features (e.g., failure to lactate, abnormal vital signs) that can not be explained by hypothyroidism alone.
Main Explanation
This patient’s clinical presentation is concerning for panhypopituitarism (given the fatigue, sleep disturbances, inability to lactate, hypotension and cold, dry skin). Given her history of severe peripartum blood loss, the diagnosis of Sheehan syndrome is most likely. likely.
Ischemia and necrosis of the anterior pituitary is the underlying mechanism for Sheehan syndrome. During pregnancy, increased circulating estrogen causes hyperplasia of lactotrophs in order to prepare for the increased hormonal demands during and following pregnancy. This increased size of the pituitary, however, is not associated with increased blood flow, which makes the pituitary gland especially susceptible to ischemia during low-volume states (e.g. prolonged or severe postpartum bleeding).
The onset of clinical features of the ensuing hypopituitarism is dependent on the severity of blood loss and can occur any time from the immediate postpartum period to years after delivery. Severe cases usually present as failure to lactate, fatigue, and lethargy within the first days or weeks after delivery. All pituitary hormonal deficiencies can occur, but the sudden onset of ACTH (and therefore, cortisol) deficiency is the most serious because it can cause life-threatening hypotension.
Diagnosis is clinical. Although prolactin levels are usually not measured, the basal levels of the other pituitary hormones are necessary. Treatment consists of lifelong hormone substitution therapy for each individual hormone that is deficient. deficient.
Major Takeaway
Sheehan syndrome is a result of ischemia and necrosis of pituitary gland that can occur in an event of profound peripartum blood loss. It clinically presents with signs and symptoms of panhypopituitarism, such as inability to lactate, amenorrhea, lethargy, fatigue and signs and symptoms of other pituitary hormone deficiencies.
References
Snyder PJ. Causes of hypopituitarism. Cooper, DS, ed. UpToDate. Waltham, MA: UpToDate Inc. https://www.uptodate.com (Accessed on December 9th, 2019.)
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The United States Medical Licensing Examination (USMLE®) is a joint program of the Federation of State Medical Boards (FSMB®) and National Board of Medical Examiners (NBME®). Osmosis is not affiliated with NBME nor FSMB.
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