A prolactinoma is the most common pituitary tumor — a benign growth that produces excess prolactin. In women it causes irregular periods, milk production, and infertility. In men it causes low testosterone and erectile dysfunction. First-line treatment is cabergoline (a twice-weekly pill), which shrinks the tumor and normalizes prolactin in 80–90% of patients.
Prolactinomas account for about 40% of all pituitary tumors and are the most common functional pituitary adenoma. Despite being brain tumors, they are benign and almost always managed successfully with medication — surgery is rarely needed.
Microadenoma vs. Macroadenoma
- Microadenoma (<10mm): Most common; rarely causes structural problems; responds very well to dopamine agonists
- Macroadenoma (≥10mm): Can compress the optic chiasm (causing vision loss or visual field defects), cause headaches, or compress normal pituitary tissue (causing deficiency of other hormones like TSH, LH, FSH, growth hormone)
What High Prolactin Does
Prolactin normally rises during pregnancy and breastfeeding to stimulate milk production. When elevated outside this context, it suppresses the hypothalamic-pituitary-gonadal axis by inhibiting GnRH pulsatility — shutting down LH and FSH release and causing:
- Women: Irregular or absent periods, galactorrhea, infertility, decreased libido, bone loss
- Men: Low testosterone, erectile dysfunction, decreased sperm production, infertility, gynecomastia
🔍 Other Causes of High Prolactin: Before assuming prolactinoma, always consider medication-induced hyperprolactinemia — antipsychotics (haloperidol, risperidone), metoclopramide, domperidone, some antidepressants, and antihypertensives can all raise prolactin. Hypothyroidism also raises prolactin (check TSH). Stress, pregnancy, and even a recent breast exam can transiently elevate prolactin.
Diagnosis
- Serum prolactin level: >200 ng/mL is virtually diagnostic of prolactinoma; 20–200 ng/mL requires further evaluation to distinguish tumor from medication/other causes
- MRI pituitary with gadolinium: Gold standard to visualize the tumor size and location
- Visual field testing: For macroadenomas near the optic chiasm
- Pituitary hormone panel: To assess if other hormones are deficient (secondary hypothyroidism, hypogonadism, growth hormone deficiency)
Treatment
Cabergoline (Dostinex) is the preferred dopamine agonist — taken twice weekly. It normalizes prolactin in 80–90% of patients, restores periods and fertility, and shrinks most tumors significantly. Bromocriptine is an alternative taken daily or twice daily; has the longest safety data in pregnancy.
| Cabergoline | Bromocriptine | |
|---|---|---|
| Dosing | Twice weekly | Daily or twice daily |
| Efficacy | Higher (~90%) | Good (~80%) |
| Tolerability | Better | More nausea/dizziness |
| Pregnancy safety data | Good (less data) | Extensive (preferred) |
Surgery (transsphenoidal resection) is reserved for: tumors not responding to medication, patients unable to tolerate medication, tumors causing acute vision loss, and personal preference.
After 2–3 years of normal prolactin and tumor shrinkage, a trial of medication tapering/discontinuation is considered in ~30–40% of patients — some achieve lasting remission.
Key Takeaways
- Prolactinomas are the most common pituitary tumor — benign and highly treatable
- High prolactin suppresses sex hormones → irregular periods/infertility in women; low T/ED in men
- First check for medication causes (antipsychotics) and hypothyroidism before diagnosing prolactinoma
- Cabergoline (twice-weekly pill) normalizes prolactin in 80–90% and shrinks most tumors
- Surgery is rarely needed — reserved for large tumors, visual problems, or medication failure
- Fertility is usually restored with treatment — bromocriptine is preferred for pregnancy
- After 2–3 years of remission, medication taper and possible discontinuation can be attempted
Our Team Can Help
All five of our providers diagnose and manage endocrine conditions.
Book an Appointment or call 832-968-7003