Endocrine Pharmacology USMLE Step 1 Practice Question

A 28-year-old woman presents to her gynecologist with a 6-month history of amenorrhea, bilateral milky nipple discharge, and inability to conceive despite 12 months of unprotected intercourse with her partner. She reports occasional frontal headaches but denies visual changes, weight gain, cold intolerance, or fatigue. She takes no medications, including hormonal contraceptives, antipsychotics, or antiemetics. Physical examination reveals bilateral expressible galactorrhea; thyroid palpation is normal, and there is no evidence of acromegaly. Vital signs are within normal limits (BP 118/76 mmHg, HR 72/min, RR 14/min, Temp 98.6°F). Laboratory workup demonstrates a serum prolactin of 85 ng/mL (normal <25 ng/mL), TSH of 1.8 mIU/L, and a negative serum beta-hCG. MRI of the pituitary gland confirms a 7-mm microadenoma with no suprasellar extension, and formal visual field testing remains intact. Which dopamine agonist is the most appropriate initial therapy?