If you’re preparing for the United States Medical Licensing Examination® (USMLE®) Step 2 exam, you might want to know which questions are most often missed by test-prep takers. Check out this example from Kaplan Medical, and read an expert explanation of the answer. Also check out all posts in this series.
A 26-year-old woman comes to the physician because of a one-year history of amenorrhea. She has had occasional discharge from both breasts. She takes no medications. She has a 5-year-old child that she breast-fed until age 9 months. There is diffuse enlargement of the thyroid gland. Breast examination shows expression of milk from both breasts. MRI of the brain shows pituitary enlargement. Laboratory studies show:
Urine beta-human chorionic gonadotropin negative.
Which of the following is the most appropriate next step in management?
D. Thyroxine replacement.
E. Transsphenoidal surgery.
The correct answer is D.
The patient has hyperprolactinemia, amenorrhea, galactorrhea, and hypothyroidism. MRI scan of the pituitary shows diffuse enlargement. The correct diagnosis is primary hypothyroidism, which is one of the functional causes of hyperprolactinemic states.
Hyperprolactinemia occurs in approximately 25% of patients with primary hypothyroidism. There will be thyrotrope-cell hypertrophy and hyperplasia and an increased level of thyrotropin-releasing hormone (TRH) because of the lack of negative feedback by thyroid hormones. TRH causes a diffuse pituitary enlargement with increased synthesis and secretion of prolactin. Thyroid hormone replacement will restore normoprolactinoma and will cause regression of the pituitary enlargement.
Choice A and B: Bromocriptine or cabergoline are both dopamine agonists used for medical treatment of prolactinoma. These medications may control the hyperprolactinemia but will not affect the primary problem, which is the primary hypothyroidism.
Choice C and E: Radiation therapy and transsphenoidal surgery are second-line treatments of hyperprolactinemia, but not hypothyroidism.
Tips to remember
- Primary hypothyroidism can present with hyperprolactinemia.
- Increased TRH stimulates the pituitary gland, causing prolactin secretion.
- Primary hypothyroidism and secondary hyperprolactinemia: Thyroid replacement therapy will correct both.
For more prep questions on USMLE Steps 1, 2 and 3, view other posts in this series.
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