The most common type of pituitary tumor is called a clinically nonfunctioning tumor, because patients do not have the classic pituitary syndromes from excess hormones, such as in acromegaly. These types of tumors may be detected during an evaluation of an incidental problem. A clinically nonfunctioning tumor may cause hypopituitarism, or an underactive pituitary gland, which may lead to failure of sexual function, reduced sperm production, and cessation of a woman's menstrual period, along with fatigue.
Another common pituitary tumor is called a prolactinoma, a benign tumor that produces the prolactin hormone. Prolactin stimulates breast milk production after childbirth. Women with a prolactinoma may have reduced or absent menstrual cycles along with breast milk production.
An uncommon pituitary tumor causes excess growth hormone production (a hormone necessary for normal childhood growth) resulting in acromegaly. In adults, such tumors lead to excessive somatic growth and multiple systemic, medical consequences. Another uncommon pituitary tumor results in Cushing's disease, a disorder of excess steroid production.
According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), autopsy studies indicate that 25% of the US population have small pituitary tumors. 40% of these pituitary tumors produce prolactin, but most are not considered clinically significant. Clinically significant pituitary tumors affect the health of approximately 14 out of 100,000 people.
