Pituitary gigantism is a rare condition whose association with McCune-Albright syndrome suggests that mutations in alpha-subunit of a Gs protein are an important cause of this condition. In addition to somatotroph adenoma, it is now recognized that somatotroph hyperplasia can also result from increased levels of growth hormone-releasing hormone. Transgenic rats with hypersomatotrophism are prone to renal and hepatic pathology.