| Abstract: | Twenty normal adult volunteers were systematically tested with five known provocative agents of human growth hormone (HGH) release in order to ascertain which procedure was the most effective stimulus for pituitary testing purposes. Ninety-five per cent responded normally (5 ng/ml increment) to levodopa (l-dopa) and 90 per cent to insulin-hypoglycemia. Arginine, vasopressin and glucagon were less potent stimuli; however, arginine (80 per cent response rate) was superior to vasopressin and glucagon (60 and 55 per cent, respectively).Nine subjects were retested with the same stimuli. Again, the incidence of normal HGH responses was highest with the l-dopa and insulin tolerance tests (100 and 89 per cent, respectively). Results with arginine, vasopressin and glucagon were significantly less consistent.Because of the important additional features of greater simplicity and safety, and until hypothalamic releasing substances become generally available, the routine use of l-dopa as a pituitary test agent warrants great attention. |
