## Why Initiate dopamine agonist therapy (cabergoline) is right The structure marked **A** is a prolactinoma — the most common functional pituitary adenoma (50% of all functional cases). This patient presents with the classic microadenoma (<10 mm) presentation in a young woman: amenorrhea, galactorrhea, and markedly elevated serum prolactin (280 ng/mL, which is virtually diagnostic). Prolactinomas are uniquely managed FIRST-LINE with dopamine agonists (cabergoline is preferred over bromocriptine due to better tolerability and efficacy). Surgery is reserved for medical therapy failure or tumors causing vision loss unresponsive to medication. The markedly elevated prolactin (>200 ng/mL) confirms prolactinoma and excludes pseudoprolactinemia from hook effect. ## Why each distractor is wrong - **Perform transsphenoidal surgical resection immediately**: Surgery is not first-line for prolactinomas. It is reserved for cases that fail medical therapy or present with severe mass effect (vision loss) not improving on dopamine agonists. This microadenoma with no mention of visual symptoms should be medically managed first. - **Obtain visual field testing and assess for bitemporal hemianopia**: While visual field testing is important in macroadenomas (>10 mm) presenting with mass effect, this patient has a 7 mm microadenoma with no neurological symptoms. Bitemporal hemianopia occurs from chiasmal compression by larger tumors, typically seen in men with macroadenomas. - **Administer bromocriptine followed by surgery if no response**: Bromocriptine is an alternative dopamine agonist but is not preferred; cabergoline is first-line due to superior efficacy and fewer side effects. The sequence implied (surgery after bromocriptine) is incorrect — cabergoline should be tried first, and surgery is only considered if medical therapy truly fails. **High-Yield:** Prolactinoma = most common functional pituitary adenoma; microadenomas in young women with amenorrhea/galactorrhea → dopamine agonist first-line (cabergoline preferred); macroadenomas in men with mass effect → assess vision, consider surgery if medical therapy fails. [cite: Robbins 10e Ch 24; Harrison 21e Ch 380]
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