1. The effect of growth hormone on bioactive IGF in overweight/obese women
- Author
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Anu V. Gerweck, Mette Bjerre, Melanie Schorr, Jan Frystyk, Miriam A. Bredella, Brian M. Russell, Karen K. Miller, and Laura E. Dichtel
- Subjects
0301 basic medicine ,medicine.medical_specialty ,Bioactive IGF ,Endocrinology, Diabetes and Metabolism ,Adipose tissue ,030209 endocrinology & metabolism ,Overweight ,Growth hormone ,03 medical and health sciences ,0302 clinical medicine ,Endocrinology ,Internal medicine ,Diabetes mellitus ,medicine ,Obesity ,Receptor ,Kinase ,business.industry ,medicine.disease ,IGF-I ,030104 developmental biology ,medicine.symptom ,business ,Hormone - Abstract
OBJECTIVE: Overweight/obesity is characterized by decreased growth hormone (GH) secretion whereas circulating IGF-I levels are less severely reduced. Yet, the activity of the circulating IGF-system appears to be normal in overweight/obese subjects, as estimated by the ability of serum to activate the IGF-I receptor in vitro (bioactive IGF). We hypothesized that preservation of bioactive IGF in overweight/obese women is regulated by an insulin-mediated suppression of IGF-binding protein-1 (IGFBP-1) and IGFBP-2, and by suppression of IGFBP-3, mediated by low GH. We additionally hypothesized that increases in bioactive IGF would drive changes in body composition with low-dose GH administration.DESIGN: Cross-sectional analysis and 3-month interim analysis of a 6-month randomized, placebo-controlled study of GH administration in 50 overweight/obese women without diabetes mellitus. Bioactive IGF (kinase receptor activation assay) and body composition (DXA) were measured.RESULTS: Prior to treatment, IGFBP-3 (r = -0.33, p = 0.02), but neither IGFBP-1 nor IGFBP-2, associated inversely with bioactive IGF. In multivariate analysis, lower IGFBP-3 correlated with lower peak stimulated GH (r = 0.45, p = 0.05) and higher insulin sensitivity (r = -0.74, p = 0.003). GH administration resulted in an increase in mean serum IGF-I concentrations (144 ± 56 to 269 ± 66 μg/L, p CONCLUSIONS: Our data suggest that in overweight/obesity, insulin sensitivity and GH have opposing effects on IGF bioactivity through effects on IGFBP-3. Furthermore, increases in bioactive IGF, rather than IGF-I concentration, predicted GH administration-related body composition changes.CLINICAL TRIAL REGISTRATION NUMBER: NCT00131378.
- Published
- 2018