The pituitary gland is a pea-sized organ within the brain. Despite its small size, the gland is involved in many important processes: it releases hormones that control other hormone-producing glands, while also producing hormones that directly affect various tissues in the body. Abnormal cell growth in the pituitary gland is called a tumor, or an adenoma. The direct cause of pituitary tumors is unknown. Tumors are named based on the type of hormone they produce in abnormally high amounts.
Prolactinomas
Prolactinomas arise when the pituitary gland develops an adenoma that produces too much prolactin. According to MedlinePlus, a prolactinoma is the most common type of pituitary tumor, accounting for nearly one-third of all pituitary tumors. Too much prolactin in a woman may result in production of a milky discharge from the breast even when not pregnant or breastfeeding -- this is called galactorrhea. Other indicators of abnormally high levels of prolactin due to a prolactinoma include vaginal dryness and irregular menstrual periods. In men, signs of a prolactinoma include a decrease in the amount of body hair and erectile dysfunction.
TSH-Secreting Adenoma
Thyroid-stimulating hormone is another hormone that is produced by the pituitary gland; when an adenoma within the pituitary starts producing excessive amounts of this hormone, the tumor is called a TSH-secreting tumor. These types of pituitary tumors result in the thyroid gland becoming overactive, a condition known as hyperthyroidism. Symptoms of hyperthyroidism, as described by the Hormone Foundation, include nervousness, a rapid heartbeat and abnormal sweatiness; this occurs because excess thyroid hormone speeds up the metabolism.
Growth Hormone-Secreting Adenoma
A growth hormone-secreting adenoma is develops when a tumor within the pituitary begins producing abnormally high amounts of growth hormone. As the name suggests, this hormone is involved with normal growth processes. When growth hormone is secreted in excessive amounts, a condition called acromegaly may develop. In children, this is called gigantism; children with gigantism may have delayed puberty or grow to be unusually tall. Other indications that a growth hormone-producing pituitary tumor has developed include deepening of the voice; enlargement of the hands, feet, nose or jaw; coarse facial features, especially seen in the nose; and thicker skin on the soles of the feet or the palms of the hands.
