Comparison of the diagnostic utility of the simplified and standard i.m. glucagon stimulation test (IMGST)

OBJECTIVE To compare the peak GH and cortisol responses to the simplified a nd standard i.m. glucagon stimulation test (IMGST) in order to determine wh ether the use of a simplified form of this test results in a loss of diagno stic utility. PATIENT AND DESIGN A retrospective study of 35 consecutive patients with pi tuitary disease who underwent a standard IMGST to measure GH (n=34) or cort isol (n=21) reserve at the programmed investigation unit of the Northern Ge neral Hospital, Sheffield, MEASUREMENTS Cortisol, glucose and GH levels were measured at baseline and 30, 60, 90, 120, 150, 180, 210 and 240 min during the standard IMGST. We us ed the hormone levels at baseline, 150 and 180 min for the simplified IMGST and compared the cortisol and GH responses achieved. RESULTS The median (range) peak GH and cortisol responses to simplified and standard IMGST were comparable 4.2 (0.5-47.5) vs 5.4 (0.5-47.5) mU/l (P=0. 75) and 635 (306-1669) vs 647 (306-1669) nmol/l (P=0.801), respectively. Us ing the standard 'cut-off' points to assess GH (9 mU/l) or cortisol deficie ncy (580 nmol/l) there was no significant loss of diagnostic utility (P = 0 .98 and P = 1.00, respectively). CONCLUSIONS The simplified and standard IMGST have a similar diagnostic uti lity, The simplified IMGST could replace the standard IMGST as a screening test for GH and cortisol reserve in pituitary disease. The insulin-induced hypoglycaemia stress test can be reserved for cases in which a second asses sment of pituitary reserve is clinically indicated or because of an indeter minate biochemical result.