Diagnosis of growth hormone deficiency after pituitary surgery: the combined acipimox/GH-releasing hormone test

OBJECTIVE Reduction of plasma free fatty acids leads to enhanced GH response after stimulation by GH-releasing hormone (GHRH). We studied the clinical usefulness of combined administration of acipimox and GHRH for the diagnosis of GH deficiency. DESIGN We evaluated 35 patients [mean age 53.0 years; mean body mass index (BMI) 26.7 kg/m(2) ] after pituitary surgery. We compared GH responses after acipimox and GHRH with the GH response during an insulin tolerance test (ITT) and, in a subgroup of 12 patients, with the GHRH/arginine test. The acipimox/GHRH test was additionally performed in 21 control subjects (mean age 53.8 years; mean BMI 24.7 kg/m(2) ). RESULTS In the patients, the mean (+/- SEM) peak GH was almost four-fold higher after acipimox/GHRH (6.94 +/- 1.07 mug/l, range 0.46-23.1; P <0.001) and after GHRH/arginine (8.32 +/- 1.23 mug/l, range 1.1-49.2; P <0.001) than after ITT (1.84 +/- 0.46 mug/l, range 0.01-11.9). According to the ITT, 29 patients were severely GH deficient (peak GH <3.0 mug/l). Peak GH levels after acipimox/GHRH in controls ranged from 7.5 to 78.4 mug/l (mean 29.3 +/- 3.5). GH peak values during the acipimox/GHRH test were significantly correlated with values from the ITT (r = 0.63, P <0.01) and GHRH/arginine test (r = 0.87, P