Differences in autonomity of growth hormone secretion in patients with acromegaly

Thirteen patients with acromegaly were subjected to the examination of autonomity in growth hormone (GH) secretion. TRH (500 mug iv), arginine (0.5 g/kg of body weight iv infusion), LH-RH (100 mug iv) and L-dopa (500 mg orally) were administered, and plasma GH was measured. Among them, 11 patients showed some response in plasma GH to at least one agent, but the other 2 cases showed no response to any of the above 4 agents. In the former 11 cases, the patients were regarded as belonging to the less autonomous type and in the latter 2, to the more autonomous type in GH secretion. Six cases (4 cases of the less autonomous and 2 cases of the more autonomous type) received an administration of 500 mug of synthetic somatostatin parenterally. Following administration of somatostatin, the patients of both types showed significant GH decrease, although GH decrease in the more autonomous type was smaller than that of the less autonomous type. These results would suggest that there might be no acromegalics secreting GH FROM THE PITUITARY WITH COMPLETE AUTONOMITY, AND THE DIFFERENCE OF AUTONOMITY IN ACROMEGALIC PATIENTS MIGHT DEPEND EITHER ON THE DIFFERENCE IN SENSITIVITY AND/OR THE NUMBER OF RECEPTORS IN THE PITUITARY RATHER THAN THOSE IN HYPOTHALAMUS TO EXOGENOUS STIMULI.