A prolactinoma is a prolactin-producing tumour of the pituitary gland, and they are the most common type of hormone-producing pituitary tumour.
- Common causes of raised prolactin
- Nipple stimulation and suckling
- Certain medications such as:
- Anti-sickness medications e.g. Metoclopramide, stemetil, Domperidone, also acid reducing medication like Omeprazole can raise your prolactin level.
- Certain antidepressants and tranquillisers used to treat mental health illness can raise prolactin: examples include Amytriptyline and Fluoxetine (Prozac) and risperidone.
- Some homeopathic and herbal medications.
- Another possibility of raised prolactin is an underactive thyroid gland, which can be diagnosed by a simple blood test and which requires treatment with thyroid hormone tablets.
Once your doctor has excluded these causes, he or she will consider the possibility of a prolactinoma.
Signs and symptoms presenting in women
Most women with prolactinomas are likely to have microprolactinomas. Your first symptoms may relate to loss of periods (amenorrhoea) as excessive prolactin interferes with the pituitary’s production of the hormones FSH and LH which control the menstrual cycle. You may have reduced interest in sex (low libido) and experience vaginal dryness and discomfort during intercourse. You may also be infertile because of impaired egg release by the ovaries -although there is usually effective treatment for this problem. You may also develop excess breast milk production (called galactorrhoea), which may leak spontaneously. This is due simply to the biological action of prolactin and is not a sign of breast disease, particularly breast cancer. Women with prolactinomas do not have any increased risk of breast cancer. Although it is tempting to look to see if it is still present, you should resist the temptation.
Signs and symptoms presenting in men
Men with prolactinomas usually have tumours larger than 10mm in diameter (macroprolactinomas). However, a larger size tumour does not rule out an excellent response to tablet treatment. As in women, excessive prolactin reduces production of FSH and LH by the pituitary gland. This in turn lowers testosterone levels and may result in a reduced interest in sex (low libido) and in impotence. Men may also have infertility due to a low sperm count. Milk production by the male breast can occur but is very uncommon even when prolactin levels are very high. Once diagnosed and treatment with medication has been established and the abnormal level of prolactin starts to decrease, the abnormally low testosterone level should in turn start to recover and rise again. This does not happen in all cases and in that instance the men will go on to have hormone replacement therapy in the form of testosterone.
How is a Prolactinoma diagnosed?
The tests to diagnose a prolactinoma are relatively straightforward and should not cause you too many problems. They consist of blood tests to check hormone levels and a scan of the pituitary gland to show the size of the prolactinoma. As mentioned previously, stress and the insertion of a needle to take a blood sample can slightly raise your prolactin level, so it requires to be repeated more than once to ensure the result is consistently high and a true value.
Another cause of raised prolactin can be a benign condition called macroprolactinaemia, which is an artefactual elevation of serum prolactin measurement, as a result of prolactin with certain blood proteins. It is of no clinical significance but must be distinguished from prolactin-producing pituitary tumours. Your GP may carry out initial tests on your prolactin and thyroid levels. You then would need to attend a specialist endocrine clinic as an outpatient for further tests, including any scans.. The other hormones produced by the pituitary will also need to be checked- this can be done by a single blood sample. Some specialists may recommend further tests to better assess pituitary gland functioning. These investigations involve timed blood sampling and possible administration of a hormone or specific drug to produce stimulation or suppression.
A scan is usually carried out to give detailed pictures of the pituitary gland. There are two types of scan: l MRI (magnetic resonance imaging, using a special magnetic technique) l CT or CAT (computerised tomography, using X-ray imaging) specific drug to produce stimulation or suppression.
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. 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. l 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. l Bromocriptine is usually given twice or three times daily (one tablet 2.5mg) l 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. Cabergoline should to be taken at night when going to bed with a light supper or snack e.g., tea/milk and a biscuit. This should reduce the chance of any unwanted effects. Your doctor will give you instructions on how to build up the dose slowly, again to minimise any side effects, particularly dizziness on standing up and headaches. Generally these side effects will diminish as your body becomes used to the medication.
Other side effects include tiredness, abdominal pain, breast discomfort and nasal congestion. Psychological disturbance may be a rare complication of either cabergoline or bromocriptine. 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 prolactinomas 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.