Prolactinoma: The Daily PANCE Blueprint

The answer is C. Cabergoline

Amenorrhea, galactorrhea, and bitemporal hemianopsia with a markedly elevated prolactin is a prolactinoma — the most common functioning pituitary tumor. Prolactin suppresses GnRH, which shuts down LH and FSH and stops the menstrual cycle, while directly driving milk production; the visual defect comes from the tumor pressing upward on the optic chiasm, where the crossing nasal fibers carrying the temporal fields are squeezed first. The most appropriate initial treatment — even for a macroadenoma with visual compromise — is a dopamine agonist, and cabergoline is preferred over bromocriptine for better tolerability and efficacy. This is the counterintuitive part and the reason the question exists: prolactinoma is the one pituitary tumor where medicine beats surgery first. Dopamine is the physiologic brake on prolactin (prolactin is unique among pituitary hormones in being tonically inhibited), so a dopamine agonist both stops the secretion and shrinks the tumor, often restoring the visual fields within weeks. Transsphenoidal surgery is the trap — it is reserved for patients who cannot tolerate or do not respond to medical therapy, or for acute apoplexy. Before you commit to the diagnosis, exclude the everyday causes of hyperprolactinemia: pregnancy, primary hypothyroidism (high TRH stimulates prolactin — hence checking the TSH), renal failure, chest wall stimulation, and dopamine-blocking drugs such as antipsychotics and metoclopramide. An oral contraceptive would mask the amenorrhea while the tumor kept growing.