Acromegaly is a medical circumstance that occurs when the anterior (rear) pituitary gland makes too much enlargement hormone (GH), after a person has passed puberty. If this occurs before puberty it causes a circumstance recognized as gigantism. A number of medical circumstances may reason the pituitary gland to make too much growth hormone, but the most general cause is a tumor on the pituitary gland called a pituitary adenoma.