A B C D E F G H I J K L M N O P R S T U V W

PROLACTINOMA

What is a Prolactinoma ?

The pituitary gland is a pea-sized structure situated behind the root of the nose and attached to the bottom of the brain. It makes a series of chemical substances (called hormones) which are released into the blood circulation. From here, the hormones have their effects on different organs and tissues. One of these hormones is called prolactin. It is responsible for stimulating milk production in women for breast-feeding their baby. Prolactin is normally produced in small quantities in non-pregnant females as well as in males, in whom prolactin probably has no function. The production is much higher during breast-feeding. A prolactinoma is a benign (non-cancerous) tumour or growth in the pituitary gland. It produces much more prolactin than normal. The bigger the tumour, the more prolactin it tends to make. Sometimes the tumour may grow as large as a bird's egg. The high level of prolactin may produce breast milk even in women who have never been pregnant. This is called galactorrhoea. The breasts may also be tender. In males, there is rarely milk production. However, prolactin seems to reduce sexual interest. This is quite a common symptom in both males and females with the disorder. Larger tumours cause effects due to their size. They may interfere with other hormones usually made by the pituitary. The main ones are those which stimulate the adrenal glands to make hydrocortisone (cortisol), and the one which stimulates the thyroid to make thyroxine. The deficiency of both of these hormones produces symptoms of tiredness and general weakness. High prolactin levels often interfere with the hormones which stimulate the ovaries and the testes to make the sex hormones. This produces infertility and poor sexual performance. Small tumours (microadenomas) do not cause pressure on surrounding structures. However, larger tumours (macroadenomas of10mm or more) can press on the optic nerves which transmit the images from the eye to the brain. This will produce a blind spot in the field of vision and may proceed to blindness if untreated.

Why does a Prolactinoma occur ?

There is no known cause for the overgrowth of prolactin-producing cells which then goes on to develop into a tumour.

Treatment Involved for a Prolactinoma

DIAGNOSIS A number of tests are used to make sure that the diagnosis is correct. In particular, a number of drugs used for other reasons can raise the blood level of prolactin. Stress, as well as the conditions of underactive thyroid and polycystic ovaries may also be a cause. High quality x-rays (CT scan) or a magnetic scan (MRI) are the best means of measuring the size of the tumour and therefore the risk to surrounding structures. Other tests are done to confirm whether there is a deficiency of other pituitary hormones.

TREATMENT In most cases, the tumour can be made to shrink with a type of drug called a dopamine agonist : the most commonly used one is bromocriptine. This is given daily in tablet form. Similar drugs (eg cabergoline) only need to be taken once or twice a week). The starting dose is very small and is taken at night with a bed-time snack. The dose is gradually increased at 1 to 2 weekly intervals. The doctor will check a blood sample regularly and will use the measured level of prolactin to decide whether an increase in dose is needed. Quite often, the level of prolactin returns completely to normal. In some cases, the tumour is large enough to justify surgery. An operation may also be needed if side-effects develop on dopamine agonist treatment, or if the reduction in tumour size is insufficient. The tumour can be operated upon either through or near the nose, or through the skull itself. This may be followed by radiotherapy to « mop up » the remaining tumour cells. Some patients will be treated with radiotherapy alone or while on dopamine agonist drugs to produce a more permanent control of the tumour. This treatment consists of a series of about 20 treatment sessions over a period of 4 to 6 weeks. The high-powered rays are focused on the pituitary gland. This treatment causes shrinkage of the prolactinoma over a period of years: this makes it possible for tablet treatment to be discontinued eventually in many patients. It is important to understand that although radiotherapy is used, these are not actually malignant growths. Pituitary tumours are one of the few types of non-cancerous growths which respond well to radiotherapy.

During Treatment for a Prolactinoma

If abnormal breast milk was present before, it soon disappears. Any breast discomfort rapidly improves too. If the tumour has affected vision, this generally improves slowly with drug therapy, and more rapidly following surgery. Repeated blood tests show that prolactin levels fall as the tumour shrinks. There may be an improvement in the level of other hormones if they were previously affected. You may develop nausea and dizziness due to the tablets used for treatment. This often occurs when the dose is given too early in the day, or is built up too rapidly. If tests show up a deficiency of other pituitary hormones, then these will need to be given. Details of such treatment are covered in a separate leaflet (hypopituitarism).

After Treatment for a Prolactinoma

Regular visits to a specialist doctor are always needed, whether or not surgery, tablets or radiotherapy have been used for treatment. About one paitent in 15 can discontinue the dopamine agonist drug in due course. Sometimes bleeding occurs into prolactinomas. This condition, called pituitary apoplexy gives a sudden headache, visual symptoms or even loss of consciousness. The doctor needs to be notified quickly.

If a Prolactinoma is Left Untreated

Small prolactinomas probably increase in size only very slowly. Some even shrink by themselves over a period of years. These could be left untreated and their growth checked regularly with appropriate scans and blood prolactin measurements. However, raised blood prolactin levels cause a lowering of sex hormone levels and both wellbeing and the bones may suffer as a consequence of this (a condition called osteoporosis). Large untreated prolactinomas may threaten eyesight and have been known to produce complete blindness.

Effects on Family of a Prolactinoma

Some patients initially come with the problems of infertility and impotence. It should be reassuring for the partner to know that these problems can usually be corrected with the right treatment.