Contributor: Christine Hulette
Benign adenomas account for the overwhelming majority of pituitary lesions and they may secrete various hormones (growth hormone, prolactin, ACTH, gonadotrophin or thyrotrophin). Prolactin secreting adenoma is the most common form and may result in galactorrhea, amenorrhea and infertility. Adenomas that secrete growth hormone result in acromegaly or rarely gigantism. ACTH producing adenomas produce pituitary dependent Cushing syndrome. Gonadotroph adenomas may result in precocious puberty. Thyrotrophin secreting adenomas are rare. 25-50% of adenomas are nonfunctional. Mixed forms occur. Small incidental adenomas are found in <20% of pituiary glands postmortem. Syndromes may be associated with a pituitary adenoma because of causal factors in the development of the adenoma (Albright syndrome, Carney complex syndrome) or because of effects of an excess secretion of pituitary hormones (Cushing syndrome, acromegaly).