Prolactinoma
A benign tumour of the pituitary gland that makes too much of the hormone prolactin. It can cause milky breast discharge, irregular or absent periods and low fertility in women, and low libido and erectile problems in men, and large tumours can press on nearby structures. It is usually very treatable with tablets.
What it is
A prolactinoma is a benign (non-cancerous) tumour of the pituitary gland, the small hormone-control gland at the base of the brain. It over-produces prolactin, the hormone that normally drives breast milk production, and is the commonest hormone-secreting pituitary tumour. High prolactin disrupts the reproductive hormones, so the effects differ by sex. In women it typically causes irregular or absent periods, reduced fertility, and sometimes a milky discharge from the breasts (galactorrhoea) unrelated to breastfeeding; because periods change early, small tumours are often found sooner. In men it tends to cause low sex drive, erectile difficulty, reduced fertility and sometimes breast enlargement or discharge, and, because these can be overlooked, men more often present later with a larger tumour. A large prolactinoma can press on surrounding structures, causing headaches or visual problems (classically loss of the outer fields of vision, from pressure on the nerves to the eyes). Diagnosis rests on finding a high prolactin level (after excluding other causes, such as certain medications, an underactive thyroid or pregnancy) together with pituitary imaging (MRI). Reassuringly, most prolactinomas respond very well to medication that lowers prolactin and shrinks the tumour, so surgery is often not needed.
Key lab markers
- Prolactin — high; the central finding, often markedly so with a larger tumour.
- FSH and LH, with estrogen or testosterone — often low or disrupted, reflecting the effect on reproductive hormones.
- TSH and free T4 — to exclude an underactive thyroid, which can raise prolactin.
- Pregnancy test — pregnancy naturally raises prolactin and must be excluded.
- Pituitary MRI — to confirm and size the tumour.
- Medication review — several drugs raise prolactin and mimic a prolactinoma.
Symptoms
- Irregular, infrequent or absent periods (women)
- Milky discharge from the breasts unrelated to breastfeeding (galactorrhoea)
- Reduced fertility
- Low sex drive and erectile difficulty (men)
- Breast enlargement or discharge (men)
- Headaches
- Visual problems, classically loss of side vision (larger tumours)
Related symptoms
Related lab panels
When to discuss with a doctor
A prolactinoma is worth considering when there is a milky breast discharge unrelated to breastfeeding, unexplained irregular or absent periods, reduced fertility, or, in men, low libido and erectile problems — especially if combined with headaches or visual changes, which suggest a larger tumour pressing on nearby structures. The work-up starts with a prolactin level, alongside checks to exclude other causes (medications, an underactive thyroid, pregnancy), and, if prolactin is genuinely high, a pituitary MRI. Most prolactinomas are very treatable with medication that lowers prolactin and shrinks the tumour, restoring periods and fertility, so it is important not to dismiss the symptoms. New visual loss with a known or suspected pituitary tumour needs prompt assessment. Mediora.AI can surface a raised prolactin, with its effect on the reproductive hormones, that points toward this treatable diagnosis; confirming it and choosing treatment belong with your endocrinologist.