Effects of gastric bypass on the GH/IGF-I axis in severe obesity -: and a comparison with GH deficiency

Objective: Overfeeding suppresses GH secretion and makes evaluation of a suspected GH deficiency (GHD) difficult. In normal weight subjects, gender is known to influence GH concentrations, which is most apparent in the ambulatory, morning-fasted state. In this study. we examined the GH/IGF-I axis in obese men and women and the effect of surgically induced weight loss. Design: Sixty-three subjects (body mass index (BMI) 45 +/-6 kg/m(2) : 54 women. 9 men) were studied prior to, and 6 and 12 months following Roux-en-Y gastric bypass (RYGBP) surgery. Fifty-four patients with classic GHD (BMI 2 +/- 6 kg/m(2) : 35 men. 19 women) were included for comparison. Methods: Hormones were analysed in fasting morning serum samples. Results: RYGBP resulted in a decreased BMI to 35 +/- kg/m(2) at 6 months and 32 +/- 6 kg/m(2) at 12 months. GH and IGF-I increased at 6 months in the women and at 12 months in both sexes by >= 300 and 11% respectively. Prior to RYGBP. GH concentrations were low in the obese men and similar to those of GHD men (mean 0.09 mU/l). Obese women had tenfold higher values than obese men and sevenfold higher than GHD women. IGF-I levels were in the low reference range in the obese and below - 2 S.D. for age in 13%. Conclusions: Surgically induced weight loss partially restores GH secretion. Despite a marked suppression of GH values, a gender influence is maintained in severe obesity In obese women, single morning GH and IGF-I values seem sufficient to exclude a suspicion of classic GHD.