Maximal secretory capacity of somatotrope cells in obesity: comparison with GH deficiency

OBJECTIVE: To evaluate the maximal secretory capacity of somatotrope cells in obesity and to compare it with that in hypopituitaric patients with GH deficiency. DESIGN: Stimulation with GHRH. (1 μg/kg iv) combined with arginine (ARG, 0.5 g/kg iv), which strongly potentiates the GH response to the neurohormone, likely inhibiting hypothalamic somatostatin. The reproducibility of the GH response to GHRH+ARG was evaluated in a second session. SUBJECTS: Forty-five patients with simple obesity (OB 11 male and 34 female, age 40.5±1.8 y, BMI 38.8±1.1 kg/m2), 49 patients with hypopituitarism (GHD, 23 male and 26 female, 43.6±2.4 y, 24.7±0.7 kg/m2) and 44 normal young volunteers (NS, 25 male and 19 female, 33.8±1.0 y, 21.6±0.3 kg/m2) were studied. MEASUREMENTS: GH levels were assayed by IRMA method, basally at −60 and 0 min, and than every 15 min up to +120 min. Basal IGF–I levels were assayed by RIA method, after acid-ethanol extraction. RESULTS: IGF–I levels in OB were lower (P