What is a Pituitary Adenoma?

Each anterior pituitary cell type may proliferate or multiply leading to a pituitary adenoma. In the case of acromegaly, a somatotroph adenoma arises from GH-producing cells and is the source of the excessive release of GH. Pituitary adenomas may also be mixed and co-secrete prolactin and GH. The mechanisms by which normal pituitary cells proliferate are not well known. Some genetic factors have been implicated, but familial acromegaly is very rare.

Pituitary adenomas are either microadenomas (tumours less than 1 cm) or macroadenomas (greater than 1 cm). They can be noninvasive (contained within the sella turcica) or invasive (extending beyond the sella).

As the adenoma grows, it may exert pressure on nearby structures within the brain, such as the optic chiasm and the normal pituitary thereby impairing its function. It may thus cause headaches, visual disturbances and abnormal pituitary function also called hypopituitarism. This is characterized by loss of strength (asthenia), low blood pressure, hypothyroidism, menstrual cycle disturbances in women and erectile dysfunction in men. When hypopituitarism is present, hormonal replacement therapy is needed.

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