What is a Prolactinoma?

A prolactinoma is a prolactin-producing tumour of the pituitary gland. This is a benign tumour, and not a brain tumour or cancer.

Doctors use the words ‘tumour’, ‘adenoma’ or ‘growth’ which means a swelling on the pituitary gland. These tumours only grow very slowly and many do not seem to grow at all. We do not know exactly what causes prolactinomas, but they are the most common type of hormone-producing pituitary tumour.

The action and stress of performing a blood test can mildly elevate the prolactin level and for this reason more than one level requires to be checked.

An appointment with an endocrinologist is usually sought by the GP, when there have been repeated raised levels of prolactin. Following referral to an endocrine department, the initial appointment will probably entail having your prolactin level re-checked.

Prolactinomas come in various sizes, but the vast majority are less than 10mm (3/8 inch) in diameter. These are called microprolactinoma. The rarer, large tumours greater than 10 mm in size are called macroprolactinoma. Prolactinomas can occur in men and women. The symptoms produced by a prolactinoma depend on the sex of the patient and the size of the tumour.

Medication treatment for prolactinoma

Whatever the size of your prolactinoma, it is likely that your treatment will be with tablets.

Drugs known as dopamine agonists are the first-line medication in patients presenting with a prolactinoma.

Medications

Cabergoline (brand name - Dostinex), Bromocriptine (brand name - Parlodel) and a third drug, Quinagolide (brand name - Norprolac) are the three available medications. All these drugs act by reducing prolactin secretion by the prolactinoma.

Cabergoline is long acting and requires one or two doses per week. The usual dose of cabergoline is one tablet (0.5mg) once or twice a week, although higher doses are occasionally required. Sometimes the dose can be reduced later during long-term treatment.

Bromocriptine is usually given twice or three times daily (one tablet 2.5mg)

Quinagolide is taken once daily, with the dose increased gradually to 75micrograms.

These drugs are safe and well tolerated by most patients. To minimise any side effects, particularly dizziness on standing up, nausea and headaches they should be taken with food.

Prolactin levels often fall to normal within a few weeks of starting the treatment. In women, once prolactin has fallen to normal, menstrual cycles usually resume; interest in sex is regained and fertility is restored in most cases. In men, testosterone levels may raise, which often improves sex drive and potency.

Nearly all prolactinoma shrink in size following treatment with the tablets. If your prolactinoma is pressing on the nerves to the eyes, there is a good chance that your vision will improve as the tumour shrinks. If you have a large prolactinoma, you may have several pituitary scans over the months and years so that the shrinkage can be assessed.

You will be reviewed by your endocrinologist. Initially, this may be every 3-6 months but once blood levels and treatment doses are stabilised you will be reviewed once a year. Obviously during this time you will be able to contact your own endocrine department should you have any problems.

Some small prolactinoma can go into remission after dopamine agonist treatment. In some patients, a trial period of withdrawal of treatment may be recommended after 3-5 years.