Prolactinoma is a condition in which a noncancerous tumor (adenoma) in the pituitary gland in your brain overproduces the hormone prolactin. The major effect of increased prolactin is a decrease in normal levels of sex hormones — estrogen in women and testosterone in men.
Although prolactinoma isn't life-threatening, it can cause vision impairment, infertility and other effects. Prolactinoma is one of several types of tumors that can develop in your pituitary gland. Some pituitary tumors may produce hormones in excess (functioning pituitary tumors), but most don't (nonfunctioning pituitary tumors).
The pituitary gland is a small bean-shaped gland located at the base of your brain. Despite its small size, the pituitary gland influences nearly every part of your body. Its hormones help regulate important functions such as growth, blood pressure and reproduction.
Doctors often are able to effectively treat prolactinoma with medications to restore your prolactin level to normal. Surgery to remove the pituitary tumor also may be an option.
The signs and symptoms of prolactinoma result from excessive prolactin in your blood (hyperprolactinemia) and, if the tumor is large, from the pressure of a pituitary tumor on surrounding tissues. Because the hormone prolactin can affect men and women differently, the signs and symptoms of prolactinoma may be unique in each.
The pituitary gland is part of your endocrine system, which consists of glands that produce hormones that regulate processes throughout your body. Besides the pituitary gland, the endocrine system includes the thyroid gland, parathyroid glands, adrenal glands, pancreas, ovaries (in females) and testicles (in men).
Prolactinoma is one type of tumor that develops in the pituitary gland. The cause of pituitary tumors remains unknown. Although these pituitary tumors are almost always noncancerous (benign), which means they don't spread to other parts of your body, they can increase in size. Because they grow in such limited space, they can compress and damage the normal pituitary tissue, interfering with hormone production. A tumor can also compress the optic nerves, slowly causing a loss of vision.
Overproduction of prolactin can result from causes other than a pituitary tumor, including:
Medications. The secretion of prolactin in your pituitary gland normally is suppressed by the brain chemical dopamine. Drugs that block dopamine production in your pituitary gland or that decrease the amount of dopamine that's stored in your brain may cause excess prolactin production, including:
Other pituitary tumors. Other tumors in or near your pituitary gland, such as nonfunctioning tumors and those that can cause overproduction of growth hormone (acromegaly) or the hormone cortisol (Cushing's syndrome), may block the flow of dopamine from your brain to your pituitary gland.
Hypothyroidism. Excess production of prolactin may occur in people with hypothyroidism — insufficient hormone production by your thyroid gland. This usually occurs only in people with longstanding untreated hypothyroidism.
Pregnancy, breast-feeding and breast stimulation. During pregnancy, a woman's prolactin level normally increases to prepare the breasts for milk production. After delivery, the prolactin level returns to normal, but increase again each time a baby feeds. Breast stimulation unrelated to pregnancy or breast-feeding may also cause breast discharge and a mild increase in the prolactin level.