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HealthInfo Canterbury

Prolactin & prolactinomas

Pupuhitanga ki te repe tupu

A cross section diagram showing optic nerve and optic chiasm connecting to the hypothalamus of the brain and pituitary gland at the back of the eyeProlactin 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 another reason. In women, this can cause missed periods, infertility or a milky discharge (called galactorrhoea) from their breasts. Not all women with galactorrhoea have high prolactin and not all women with high prolactin have galactorrhoea.

Men might have no symptoms from high prolactin, or they might have a lower sex drive, impotence and infertility.

Causes of high prolactin

Many things can cause high prolactin:

Other things that can cause high prolactin include:

Prolactinomas

About one-third of pituitary tumours are prolactinomas. Small ones are often found 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 your 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 there's 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. It's important to find out which tumour it is because other tumours are treated differently.

Diagnosing high prolactin

High prolactin is diagnosed by measuring your prolactin level with a blood test. You may need to stop certain medications before the blood test so it's important to tell your doctor about all the medications that you're taking. You may also need to repeat the test since blood tests can sometimes show falsely high prolactin levels.

If the blood test shows you have high prolactin, you may need to see a specialist, and they may arrange an MRI scan.

Treating high prolactin

If your prolactin level is only slightly high and you have normal periods, you may not need treatment. If the high prolactin level is caused by pregnancy, breastfeeding or medications, the only treatment you're likely to need is to consider changing the medications that are causing it.

Prolactinomas are usually treated with 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. As well as reducing prolactin levels, these drugs cause prolactinomas to shrink. So, surgery isn't usually needed, even when the prolactinoma is large and affecting your vision.

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. 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.

Small tumours are treated in women until they reach menopause. Men and women with large tumours might need lifelong treatment.

Side effects of treatment

Like all medicines, those used for high prolactin have side effects. Common ones are:

  • nausea (feeling sick)
  • feeling faint when you stand up
  • a stuffy nose
  • constipation
  • cold hands and feet
  • alcohol intolerance.

You can reduce any 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 June 2023.

Sources

Page reference: 70674

Review key: HIPRL-70674