Prolactinoma is a benign tumor of the pituitary gland, which produces large amounts of a hormone known as prolactin. To understand the issue, it is necessary to mention some facts about the hormonal function of the pituitary gland.
Pituitary gland is a small part of the brain, which, however, produces a large number of hormones including the prolactin. Above the pituitary gland, there is a part of brain known as hypothalamus, which controls the production of hormones within the pituitary gland. In case of prolactin production, hypothalamus acts as an inhibitor. Hypothalamus produces a substance known as dopamine, which inhibits the prolactin formation.
In normally produced amount, the prolactin is responsible for proper function of sex hormones, especially during pregnancy and its serum levels increase after the childbirth to allow the breastfeeding.
The cause of prolactinoma occurrence is not entirely clear. It is a benign tumor, which grows from pituitary cells forming prolactin. Therefore, prolactin levels start to increase disproportionately.
Scheme - brain with hypophysis
High levels of prolactin have paradoxically detrimental effects on the secretion of sex hormones. In men, there is a loss of sex drive and development of impotence. Women experience irregularities of the menstrual cycle and infertility. Rarely and in high serum concentration, the prolactinoma may cause enlargement of male breasts (gynecomastia). In both sexes, the prolactinoma may be accompanied by milk secretion from the breast glands.
When the prolactinoma is large, its mass may compress the optic nerves that run in the vicinity of the pituitary gland causing visual disorders. Medical textbooks usually mention failure of the external visual field of both eyes, but the disorder may actually be much variable including total blindness.
We may found high levels of prolactin in blood samples and the tumor itself can be found by imaging methods such as computed tomography or magnetic resonance imaging. Disorders of vision usually lead to an ophthalmologic examination.
Although the majority of pituitary gland tumors are treated surgically, the prolactinoma is a different issue. It is primarily treated pharmacologically, i.e. by drugs. The most effective are substances containing the dopamine, which in our body inhibits the prolactin formation. The therapy by dopamine not only decreases the production of prolactin, but also causes a significant shrinkage and disappearance of the tumor mass. If the tumor can not be handled by drug, neurosurgical approach or local irradiation is necessary.