A prolactinoma is a benign (noncancerous) tumor of the pituitary gland, which produces a hormone called prolactin. A prolactinoma is the most common type of
pituitary tumor. Symptoms are caused by too much prolactin in the blood (a condition called hyperprolactinemia) or by pressure of the tumor on surrounding tissues.
Autopsy studies indicate that 25 percent of the American population has small
pituitary tumors. Forty percent of these produce prolactin, but most are not considered clinically significant. Clinically significant pituitary tumors such as prolactinomas affect the health of approximately 14 out of 100,000 people.
Understanding the Pituitary Gland
The pituitary gland, sometimes called the master gland, plays a critical role in regulating growth and development, metabolism, and reproduction. The pituitary gland produces a number of key hormones, including:
- Prolactin, which stimulates the breasts to produce milk during pregnancy. After delivery of the baby, a mother's prolactin levels fall unless she breastfeeds her infant. Each time the baby nurses, prolactin levels rise to maintain milk production.
- Growth hormone, which regulates growth.
- ACTH (adrenocorticotropin), which stimulates the adrenal glands to produce cortisol.
- Thyrotropin, which signals the thyroid gland to produce thyroid hormone.
- Luteinizing hormone and follicle-stimulating hormone, which regulate ovulation and estrogen and progesterone production in women, and sperm formation and testosterone production in men.
The pituitary gland sits in the middle of the head in a bony box called the sella turcica. The eye nerves sit directly above the pituitary gland. Enlargement of the gland can cause localized symptoms, such as
headaches or visual disturbances.
