What causes Growth hormone secreting pituitary tumors?
GH-secreting pituitary tumors are monoclonal, indicating that a spontaneous somatic mutation is a key event in neoplastic transformation of somatotrophs. Further studies have clarified the nature of the mutation in some GH tumors that appear to have an altered stimulatory subunit (G S ) of the G-proteins that regulate adenylate cyclase activity. In a mutated cell, alterations in the G S subunit cause autonomous adenylate cyclase activity and elevated secretion of GH. However, the mutant G S is found only in about 40% of patients with acromegaly. The mechanism of GH regulation and tumor growth differs in other patients with acromegaly.