Growth hormone releasing factor-test in acromegaly: comparison with other dynamic tests

Human pancreatic growth hormone releasing factor (hpGRF1-44) was given intravenously as a 100 micrograms bolus to 20 patients with active acromegaly. The GH-responses were variable, ranging from an increase of 8 to 2813% from the basal level (mean +/- SE, 428 +/- 136%). Sixteen GRF-responders (delta% greater than or equal to 100%) were arbitrarily distinguished from four GRF non-responders, whose GH-levels increased less than 100% from basal level after GRF-administration. The outcome of the GRF-test did not correlate with the results of other dynamic tests of GH-secretion in acromegaly (oral glucose tolerance test, insulin hypoglycaemia, TRH-, LHRH-, CRF-stimulation). In 10 patients who had not been treated before, the GH-increments after GRF were higher than those in seven patients who had previously been subjected to transsphenoidal surgery, though they still had clinically and biochemically active acromegaly. Ten acromegalics, who were tested with GRF, were later treated surgically by the transsphenoidal route and were reevaluated with GRF-stimulation 2 months after surgery. Eight patients appeared clinically cured of whom four had complete normalization and four had significantly lower basal and conventionally stimulated GH-levels postoperatively. These patients also had normal postoperative GH-responses to GRF, which had been significantly higher before surgery compared with normal controls. It is concluded that the GRF-test in acromegaly does not help in establishing the diagnosis. The normalization of the GH-response to GRF after transsphenoidal surgery seems to represent additional evidence for normalization of GH-secretion, though the latter is not proven by the normal outcome of this test.