Definition of Prolactinoma:

A prolactinoma is a noncancerous pituitary tumor that produces a hormone called prolactin. This results in too much prolactin in the blood.

Causes, incidence, and risk factors:

Prolactin is a hormone that triggers lactation or milk production.

Prolactinoma is the most common type of noncancerous pituitary tumor (adenoma), making up at least 30% of all pituitary adenomas.

Prolactinomas occur most commonly in people under age 40. They are about five times more common in women than men, but are rare in children.

At least half of all prolactinomas are very small (less than 1 cm or 3/8ths of an inch in diameter). These microprolactinomas are more common in women. Many small tumors remain small and never get larger.

Larger tumors, called macroprolactinomas, are more common in men. Prolactinomas in men tend to occur at an older age and can grow to a large size before any symptoms appear.