A 28-year-old woman presents with secondary amenorrhea, galactorrhea, and infertility. MRI shows a 6 mm pituitary adenoma. Serum prolactin is 180 ng/mL. The drug of choice and mechanism of action is:
- A Bromocriptine — dopamine D2 receptor agonist suppressing prolactin secretion ✓
- B Cabergoline — dopamine D1 receptor agonist reducing tumor size
- C Octreotide — somatostatin analogue inhibiting prolactin release
- D Bromocriptine — serotonin antagonist at the lactotroph level
Explanation
Cabergoline is actually now the preferred dopamine agonist for microprolactinomas due to superior efficacy, better tolerability, and once- or twice-weekly dosing compared to bromocriptine. However, bromocriptine remains widely used and its correct mechanism is D2 receptor agonism at lactotroph cells, directly suppressing prolactin synthesis and secretion and causing tumor shrinkage. Cabergoline also acts via D2 receptors but has longer half-life. Octreotide is used for acromegaly (GH-secreting adenomas). The answer reflects that among the options, only option A correctly identifies the mechanism (D2 agonism suppressing prolactin), even if cabergoline is preferred clinically.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.