Professor Julian Davis
University of Manchester

A Prolactinoma is a Prolactin-secreting Pituitary tumour which is usually benign. It causes an increase in prolactin released into the blood (Hyperprolactinaemia). (The normal level is <500 mU/l, which can increase with stress.) Other causes of increased prolactin may be drug side-effects, Hypothyroidism, and polycystic ovary syndrome. In some cases, no cause is identified; this is termed Idiopathic.

This over-secretion of prolactin causes lactation in women, and disruption to the menstrual cycle. Men may become impotent, have a reduced libido and suffer Hypogonadism. The tumours can also cause headaches and visual disturbances. The tumours tend to be smaller in women than in men.

Prolactinomas are usually treated by drug therapy. Dopamine agonists like Bromocriptine, cabergoline and quinagolide are used to reduce the tumour size and relieve the symptoms. This is usually successful in 80% of patients. The side-effects of these drugs include nausea, vomiting, dizziness, reduced blood pressure and mood changes; these effects tend to reduce in time.

After treatment, 90% of women recover their menstrual cycle. Although men respond well, many still require Testosterone replacement.

Surgery is not a standard treatment, but debulking of a large tumour may be required if attempts to shrink it by drug therapy fail. Radiotherapy can be used to stop the tumour growing, but this is a slow process and tends to shrink the rest of the pituitary. A small tumour in a post-menopausal woman may sometimes be left untreated, but tumour size will still need monitoring.

Many issues have been raised relating to prolactinomas, the main one being weight change. Raised prolactin has been linked to weight gain, and when prolactin levels are normalised weight loss has been reported. The drug therapy used has also been reported to reduce weight. Other issues include hormone replacement therapy, and what happens to prolactin levels during the menopause. Dopamine agonists (drug therapy) should suppress the prolactin levels to normal, to allow the ovaries to function. During the menopause, Oestrogen replacement may be required. However, there are indications that oestrogen replacement therapy can sometimes cause tumour enlargement.

When a patient comes off long-term dopamine agonist therapy, there is normally a rise in prolactin levels, and tumours can re-expand. In some patients, prolactin levels remain normal. These patients are closely followed-up and monitored for pituitary under-activity. If pituitary under-activity occurs, then hormone supplements may be required. These may include corticosteroids, Thyroxine, Growth hormone or oestrogen/testosterone.

Prolactinomas are not normally hereditary.