HealthInfo Canterbury
Prolactin & prolactinomas
Prolactin is a hormone you make in your pituitary gland, a small gland at the base of your brain. One of its main roles is to help women make breast milk.
When women are pregnant, their prolactin level goes up and stays high while they're breastfeeding. Their periods often stop while they're breastfeeding. This is also caused by high prolactin. Some women seem more or less sensitive to prolactin, which probably explains why some women get their periods back earlier than others.
Sometimes your prolactin level might rise for some other reason. In women, this can cause missed periods, infertility or a milky discharge (called galactorrhoea) from their breasts. Not all women with galactorrhoea have a high prolactin and not all women with a high prolactin have galactorrhoea.
Men might have no symptoms, or they might have a lower sex drive, impotence and infertility.
A high prolactin level can also affect bones and muscles in both men and women. So, it's always important to get it checked by a specialist.
Other causes of high prolactin
Many things can cause high prolactin. Stress can make it rise briefly. Some medicines can also make it rise. These include drugs used for some psychiatric conditions, pain medicines like morphine, antidepressants, anti-nausea drugs and some blood-pressure medicines.
Other things that can cause high prolactin include:
- liver and kidney disease
- epileptic seizures
- an under-active thyroid (hypothyroidism)
- polycystic ovary syndrome
- a chest injury or skin conditions on the chest such as shingles.
Sometimes prolactin-making cells form a small growth or tumour in the pituitary gland. These are almost always benign (not cancer). Pituitary cancer is very rare. Pituitary tumours that make prolactin are called prolactinomas (pro-lac-tin-o-mas).
Prolactinomas
About one-third of pituitary tumours are prolactinomas. We often find small ones in women with galactorrhoea or with irregular or no periods. Small pituitary tumours (less than 1 cm) are called microprolactinomas (mi-cro-pro-lac-tin-o-mas). Larger ones are called macroprolactinomas (mac-ro-pro-lac-tin-o-mas).
If the tumour gets bigger, it may press on eye nerves making you lose your peripheral vision (what you can see at the edge of your vision). It can also affect the other hormones your pituitary gland makes.
Very rarely, a prolactinoma may spread and cause double vision and other problems. Only about 5% of small tumours get bigger even if left alone, but we have no way of telling which will get bigger and which won't. Men tend to have larger and more aggressive tumours than women.
Sometimes, other pituitary tumours can cause an increase in prolactin. It can be hard to tell which sort of tumour it is, but prolactin levels are usually higher in a prolactinoma. We need to know which tumour it is because we treat other tumours differently.
Treatment
We treat most people with a high prolactin level if it isn't caused by pregnancy, breastfeeding or medications. But we don't treat women with slightly high prolactin who have normal, regular periods.
We usually use drugs called dopamine agonists. The two most common ones are cabergoline and bromocriptine. Cabergoline is newer and has fewer side effects. You usually take cabergoline only once or twice a week. With larger tumours, you might need a higher dose of these drugs.
Your prolactin level usually goes back to normal when you're being treated. If you're a woman, regular periods return and breast milk disappears. You're also more likely to get pregnant. If you don't want to get pregnant, you'll need effective contraception, which you might not have needed before.
A few people need surgery because the drugs don't shrink their tumours.
We treat small tumours in women until menopause, while men and women with large tumours might need lifelong treatment.
Most women don't need treatment while they're pregnant or breastfeeding. Women usually stop taking the medicine as soon as they know they're pregnant. Some pregnant women need to be checked every three months but will restart treatment only if the tumour is growing. In 25% to 30% of women, their prolactin level will actually return to normal after pregnancy.
Side effects of treatment
Like all medicines, those used for high prolactin have side effects. Common ones are:
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You can reduce nausea by taking the medicine with food and building up the dose gradually. The side effects are less common with cabergoline than with bromocriptine.
Because bromocriptine has been available since the 1970s, we know it's safe during early pregnancy. We don't have as much evidence for cabergoline, but there doesn't seem to be a risk to babies whose mothers were taking cabergoline when they were conceived.
Written by the Department of Endocrinology, Christchurch Hospital. Adapted by HealthInfo clinical advisers. Last reviewed March 2020.
Tablets Image courtesy of voraom FreeDigitalPhotos.Net.
Review key: HIPRL-70674
