Prolactinoma: symptoms, treatment and fertility

Prolactin interferes with the pituitary hormones FSH and LH that control the menstrual cycle and, in men, testosterone production. That explains most symptoms. The Pituitary Foundation notes that symptoms depend on sex and on tumour size.

In women, first symptoms are often loss of periods, then reduced interest in sex, vaginal dryness, difficulty conceiving and milk production from the breasts, called galactorrhoea. The charity says this is not a sign of breast disease and that women with prolactinomas do not have an increased risk of breast cancer. It also advises resisting the urge to check or express milk, because stimulation can keep prolactin raised.

Men with prolactinomas usually have larger tumours. Low testosterone may cause reduced sex drive, erectile problems and a low sperm count. Patient.info adds that in men the effects are subtle and slow, presentation is often late, and bone thinning may already be present at diagnosis.

• Missed, infrequent or absent periods.

• Milk leakage from the breasts when not pregnant or breastfeeding.

• Reduced sex drive, vaginal dryness or erectile difficulties.

• Difficulty getting pregnant or a low sperm count.

• Headache and changes to vision, which suggest a larger tumour.

• In children, growth problems or delayed puberty, per Patient.info.

Not everyone needs treatment. Patient.info says asymptomatic patients do not have an absolute requirement for treatment, with indications being the effects of tumour size or of raised prolactin. For most people with symptoms, the first choice is medication.

The Pituitary Foundation says drugs known as dopamine agonists are first-line: cabergoline, bromocriptine or quinagolide. Cabergoline is long acting and taken once or twice a week, usually with food and at bedtime. Dose is built up slowly to reduce dizziness, nausea and headache. Prolactin often falls to normal within a few weeks, periods usually return, fertility is restored in most cases and testosterone may rise in men.

Nearly all prolactinomas shrink on tablets, and if a tumour is pressing on the eye nerves, vision is likely to improve. Both sources warn about impulse control problems, including pathological gambling and hypersexuality, and Patient.info adds sleepiness, so family should be told to watch for unusual behaviour. Patient.info describes monitoring for heart valve and other fibrosis, with less risk at these doses than in Parkinson's disease.

Surgery and radiotherapy are used much less now. The charity says surgery may be needed if the tumour does not shrink with tablets or side effects are intolerable, and is performed through the nose using a microscope or endoscope. Hormone replacement may be needed if other pituitary functions remain underactive.

The pituitary gland is a pea-sized gland under the brain that controls many other hormone glands. It makes prolactin, sometimes called the "milk hormone" because it stimulates milk production after childbirth, but it is also produced in men in smaller amounts. A prolactinoma is a small growth of prolactin-making cells.

The Pituitary Foundation says prolactinomas are the most common type of hormone-producing pituitary tumour, that they can occur in men and women, and that nobody knows exactly what causes them. Patient.info's professional reference estimates that prolactinomas make up about 40% of all pituitary tumours.

Size is the key distinction. The charity says the vast majority are smaller than 10 mm and are called microprolactinomas. Larger tumours are macroprolactinomas. Patient.info states that microprolactinomas rarely grow into macroprolactinomas, and that 90-95% of prolactinomas never increase in size.

The Pituitary Foundation lists several common reasons for a raised prolactin level: pregnancy, nipple stimulation, stress, an underactive thyroid gland, and certain medicines. The medicines it names include some anti-sickness drugs, acid-reducing medicines and certain antidepressants and tranquillisers.

Another benign cause is macroprolactinaemia, a measurement artefact in which prolactin attaches to blood proteins. The charity says it has no clinical significance but must be told apart from a true tumour. Patient.info suggests suspecting it when prolactin is high but there are no symptoms, and says the laboratory can treat the sample to check.

Only once these causes are excluded do doctors consider a prolactinoma. This is why a repeat blood test and a thyroid check come before any scan.

Diagnosis consists of blood tests and a scan. The Pituitary Foundation says a GP may begin with prolactin and thyroid levels, with a specialist endocrine clinic doing further tests. Because stress and the needle itself can slightly raise prolactin, the sample is repeated to make sure it is consistently high.

Patient.info says that a mildly raised prolactin should be repeated before referral and that a level above 5000 mU/L usually indicates a true prolactinoma. It also notes a laboratory pitfall, the high-dose hook effect, where a very large tumour can give a falsely low result unless the sample is diluted.

MRI is the scan of choice, as the Pituitary Foundation explains, sometimes with contrast dye. If the tumour is large, eyesight and visual fields are checked by an eye specialist, and other pituitary hormones are tested. A bone density scan may be recommended for women who have not had periods for a year and for men with prolonged low testosterone.

Treatment often restores fertility quickly, so the Pituitary Foundation advises discussing effective contraception before medication starts if pregnancy is not wanted. If pregnancy is planned, it recommends pre-pregnancy advice from an endocrinologist, and says it is normally recommended to stop medication once pregnancy is established, on specialist advice.

Patient.info says tumours can enlarge in pregnancy, particularly macroadenomas, with about a third enlarging, and that headache or visual disturbance needs urgent referral. The Pituitary Foundation notes that prolactin blood levels are unhelpful in pregnancy because they rise normally, and that there is good safety data for babies conceived on dopamine agonists. Breastfeeding plans should be discussed with the endocrinologist during pregnancy.

For most people the outlook is good. Patient.info says microprolactinomas spontaneously resolve in around a third of women, especially after the menopause or pregnancy, and that it is reasonable to try stopping medication after three years if prolactin is normal and the tumour has markedly shrunk. Follow-up is essential, because recurrence is possible. Five-year recurrence rates quoted range from 26% to 78% depending on tumour size and whether a remnant is visible on MRI.

Bone health deserves attention. Patient.info says bone loss occurs in about 25% of women with hyperprolactinaemia and does not necessarily improve when prolactin returns to normal, so bone density checks may be offered. Long-term, many people take a small dose of tablets for years and have periodic blood tests and scans.

See a GP about missed periods, milk leakage, or sexual or fertility problems. Seek urgent help for a sudden severe headache with visual disturbance, double vision or collapse, which can signal pituitary apoplexy, a rare bleed into the pituitary. Patient.info lists it among the possible complications of larger tumours.

The Pituitary Foundation also says to report any clear watery fluid from one or both nostrils to your doctor straight away, as it could be leaking spinal fluid. Call 999 for sudden severe symptoms and NHS 111 if unsure.

The Pituitary Foundation says your GP may carry out initial tests of prolactin and thyroid levels, and that you would then attend a specialist endocrine clinic as an outpatient for further tests, including any scans. Patient.info advises repeating a mildly raised prolactin before referral and referring urgently if there are headaches or visual disturbance.

Private endocrinology consultations, hormone tests and MRI scans are available, and can be quicker for a first opinion. Cabergoline and other dopamine agonist treatment is prescription-only, and long-term monitoring is normally shared between an endocrinologist and your GP. Ask for copies of your prolactin results and scan reports so that your records stay in one place.