High prolactin and prolactinomas Pupuhitanga ki te repe tupu

Your pituitary gland is a small gland at the base of your brain that sits in behind the bridge of your nose. It produces a range of hormones including prolactin. This hormone plays a role in overall health and sexual function in both men and women. One of its main roles is to help women make breast milk. Sometimes your body can produce too much prolactin, which can lead to a range of health problems. 

Many things can cause high prolactin including:

• pituitary gland tumours called prolactinomas — these are usually not cancerous
• stress
• some medicines including drugs used for some psychiatric conditions, pain medicines like morphine, antidepressants, anti-nausea drugs and some blood-pressure medicines
• liver and kidney disease
• epileptic seizures
• an underactive thyroid (hypothyroidism)
• a chest injury or skin conditions on the chest such as shingles.

Prolactinomas

About one third of pituitary tumours are prolactinomas. These tumours produce prolactin.

If a prolactinoma gets big enough, it may:

• press on the part of your brain where nerves that control vision are — this can mean you lose your peripheral vision (the edges of your vision)
• affect the other hormones your pituitary gland makes.

Only about 5% of small tumours get bigger even if left alone, but there is no way of telling if they will get bigger or not. Men tend to have larger and more aggressive prolactinomas than women.

Sometimes, other types of 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 is important to find out which tumour it is because they are treated differently.

You may have only mild or no symptoms. But high prolactin may lead to:

• infertility
• loss of interest in sex
• weaker bones than normal (osteopenia).

Women are more likely to have high levels of prolactin than men. For women, symptoms may include:

• milky discharge from your nipples when you are not pregnant or breastfeeding (galactorrhea)
• irregular periods or missed periods
• pain during penetrative sex due to vaginal dryness.

For men, symptoms of high prolactin may include:

• problems getting or keeping an erection (erectile dysfunction)
• low levels of testosterone
• enlarged breast tissue.

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 is important to tell your healthcare provider about all the medications you are taking. You may also need to repeat the test because 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 doctor (an endocrinologist), and they may arrange an MRI scan to check for tumours.

If your high prolactin is caused by medications, the only treatment you are likely to need is to consider changing your medications.

For women, you are not likely to need treatment if:

• your prolactin level is only slightly high and you have normal periods
• your high prolactin level is caused by pregnancy or breastfeeding.

Treating prolactinomas

Prolactinomas are usually treated with drugs called dopamine agonists. The most common one is cabergoline.

Cabergoline — My Medicinesexternal link

You usually take cabergoline only once or twice a week. As well as reducing prolactin levels, it causes prolactinomas to shrink. So, surgery is not usually needed, even when the prolactinoma is large and affecting your vision.

Your prolactin level usually goes back to normal when you are being treated. 

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

If you are a woman, taking a dopamine agonist will make your periods more regular and any breast milk will disappear. You are also more likely to get pregnant than before your treatment. If you do not want to get pregnant, you will need to use contraception, which you might not have needed before. 

Most women do not need treatment while they are pregnant or breastfeeding. Women usually stop taking the medicine as soon as they know they are pregnant.

Side effects of treatment

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

• feeling sick (nausea)
• 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. Your healthcare provider will give you advice about this.

The safety of taking cabergoline in early pregnancy is not certain. But research shows there does not seem to be any risk to babies whose mothers were taking cabergoline when they were conceived.