Prolactin is a hormone that induces lactation or milk formation. The size of the prolactinoma correlates with the excess prolactin level; the larger the tumor, the higher the level of prolactin that is secreted.

Prolactinoma is the most common type of pituitary adenoma and is also referred to as a prolactin -secreting adenoma of the pituitary. These tumors account for at least 30% of all pituitary adenomas. At least half of all prolactinomas are microadenomas. Microprolactinomas are more common in women. Larger tumors, called macroprolactinomas, are more common in men. Many of the smaller tumors do not appear to progress to larger tumors.

Prolactinomas occur most commonly in those under 40 years old. They are rare in children. These tumors are about fives times as common in women as men. In women, prolactinomas typically cause amenorrhea (lack of menstruation) and galactorrhea (milk production from the breasts, not associated with pregnancy) and occur in young patients. By contrast, prolactinomas in men occur in older patients and can grow to a large size before any symptoms occur.

In women:

• Cessation of menses not related to menopause
• Abnormal milk flow from the breast not related to nursing or childbirth (galactorrhea)
• Infertility
• Decreased sexual interest
• headache
• visual changes

In men:

• Enlargement of breast tissue (gynecomastia)
• Infertility
• Impotence
• Decreased sexual interest
• headache
• visual changes

Note: there may be no symptoms, particularly in men.

• Prolactin levels
• Cranial MRI or cranial CT scan that shows a pituitary mass
• Decreased testosterone levels in men

In women, the symptoms of infertility, irregular menstruation, loss of sexual interest, and milk flow not related to childbirth or nursing can be improved with treatment. Men should be treated when decreased sexual drive, infertility, or impotence occur.

Bromocriptine (a dopamine-increasing medication) is a medication used to return prolactin levels to normal in both men and women. Higher levels of dopamine can reduce prolactin levels. Larger tumors or those resistant to bromocriptine may respond to surgical removal, stereotactic radiosurgery (use of radiation aimed precisely at the tumor) or a combination of treatments.

The outlook depends heavily on the success of medical and surgical therapies. Tests to scan for recurrence following treatment are important.

Tumor regrowth is the main complication. If untreated, tumor growth may result in permanent visual loss, including blindness, because large tumors in this area often press on the nerves involved in vision.

See your health care provider if symptoms suggestive of prolactinoma develop.

If you have had a prolactinoma in the past, call your health care provider if you experience recurrence of the symptoms.