A 28-year-old woman with a 3-year history of secondary amenorrhea is diagnosed with hyperprolactinemia (prolactin 85 ng/mL) due to a microprolactinoma. She desires fertility. What is the drug of choice for her treatment?

Explanation

## Hyperprolactinemia and Microprolactinoma: Drug of Choice This patient has **secondary amenorrhea due to prolactin-secreting pituitary adenoma (microprolactinoma)** with a desire for fertility. The dopamine agonist is the first-line treatment. ### Dopamine Agonists: Cabergoline vs. Bromocriptine | Feature | Bromocriptine | Cabergoline | |---------|---------------|-------------| | **Dopamine D~2~ receptor affinity** | Lower | Higher (selective D~2~ agonist) | | **Prolactin suppression** | Effective but slower onset | Faster, more potent suppression | | **Frequency of dosing** | Twice daily | Twice weekly | | **Side effects** | GI upset, orthostatic hypotension, headache (more common) | Fewer side effects, better tolerability | | **Pregnancy safety** | Safe (long track record) | Safe; preferred in modern practice | | **Fertility restoration** | Yes | Yes | | **First-line status (current)** | Older agent, less preferred | **Preferred first-line** | **High-Yield:** Cabergoline is now the **preferred dopamine agonist** for prolactinomas because of: - Superior efficacy (higher D~2~ selectivity) - Better tolerability (fewer GI and CNS side effects) - Convenient twice-weekly dosing - Excellent safety record in pregnancy (when needed) ### Mechanism Dopamine agonists **inhibit prolactin secretion** from lactotroph cells, allowing: - Restoration of GnRH pulsatility - Recovery of gonadotropin secretion (LH, FSH) - Resumption of ovulation and menstruation - Restoration of fertility **Clinical Pearl:** Prolactin levels typically normalize within 2–4 weeks of cabergoline initiation, and menses usually resume within 2–3 months. Microprolactinomas rarely require surgery; medical management is first-line. ### Why NOT Other Options? **Estrogen + progestin OCP:** Contraindicated in active prolactinoma because estrogen stimulates further prolactin secretion and may enlarge the adenoma. OCPs are used only *after* dopamine agonist therapy has normalized prolactin levels. **Bromocriptine:** Effective but less preferred than cabergoline due to higher side-effect burden and less convenient dosing. Still acceptable if cabergoline is unavailable or contraindicated. **Metformin:** Used for PCOS-related amenorrhea, not for hyperprolactinemia. No role in prolactinoma management. [cite:Harrison 21e Ch 375; Williams Obstetrics 26e Ch 32]