A 32-year-old woman with secondary infertility presents with a 2-year history of amenorrhea. Investigations reveal elevated prolactin (68 mIU/L), normal TSH, and MRI showing a 8 mm microprolactinoma. What is the drug of choice for medical management of this condition?

Explanation

## Medical Management of Prolactinoma **Key Point:** Cabergoline is the preferred first-line dopamine agonist for prolactinoma because of superior efficacy, tolerability, and lower side-effect profile compared to bromocriptine. ### Pathophysiology of Prolactinoma-Induced Infertility Elevated prolactin suppresses GnRH secretion → ↓ FSH/LH → anovulation and amenorrhea → infertility. ### Dopamine Agonists: Mechanism Dopamine inhibits prolactin release from lactotroph cells. Dopamine agonists restore dopaminergic tone: - **Bromocriptine:** Ergot-derived, D2 agonist (older agent) - **Cabergoline:** Non-ergot, selective D2 agonist (newer, preferred) ### Comparative Efficacy & Safety | Parameter | Bromocriptine | Cabergoline | |-----------|---------------|-------------| | **Prolactin normalization** | 50–80% | 80–90% | | **Tumor shrinkage** | 50–60% | 60–70% | | **Dosing frequency** | 2–3× daily | 2× weekly | | **GI side effects** | Common (nausea, vomiting) | Rare | | **Cardiovascular effects** | Hypotension, tachycardia | Minimal | | **Ergot-related toxicity** | Fibrosis risk (long-term) | No fibrosis risk | | **Patient compliance** | Poor (frequent dosing) | Excellent | | **Cost** | Lower | Higher | **High-Yield:** Cabergoline is superior because: 1. **Twice-weekly dosing** vs. bromocriptine's 2–3× daily → better compliance 2. **Better tolerability** — fewer GI and cardiovascular side effects 3. **No ergot-related fibrosis** with long-term use 4. **Higher normalization rates** of prolactin and tumor shrinkage ### Dosing - **Cabergoline:** Start 0.25 mg twice weekly; titrate up to 0.5–1 mg twice weekly - **Bromocriptine:** Start 1.25 mg at bedtime; titrate up to 5–15 mg/day in divided doses ### Clinical Pearl **Microprolactinomas** (< 10 mm) respond excellently to medical therapy alone; surgery is reserved for: - Macroadenomas (> 10 mm) with mass effect - Medical therapy failure or intolerance - Apoplexy or visual field defects ### Monitoring - **Prolactin levels** at 2–4 weeks, then monthly until normalized - **MRI** at 6–12 months to assess tumor shrinkage - **Menstrual cycles** typically resume within 2–3 months of prolactin normalization **Warning:** Do NOT use dopamine antagonists (metoclopramide, domperidone) — they will worsen hyperprolactinemia and infertility by blocking dopamine.