Effect of Weight Loss on Free Insulin-Like Growth Factor-I in Obese Women With Hyposomatotropism
Version of Record online: 6 SEP 2012
2007 North American Association for the Study of Obesity (NAASO)
Volume 15, Issue 4, pages 879–886, April 2007
How to Cite
Rasmussen, M. H., Juul, A. and Hilsted, J. (2007), Effect of Weight Loss on Free Insulin-Like Growth Factor-I in Obese Women With Hyposomatotropism. Obesity, 15: 879–886. doi: 10.1038/oby.2007.607
- Issue online: 6 SEP 2012
- Version of Record online: 6 SEP 2012
- Received for review July 05, 2006, Accepted in final from October 31, 2006
- growth hormone;
- weight loss;
- insulin-like growth factors;
- visceral obesity
Objective: It has been hypothesized that increased free insulin-like growth factor (IGF)-I levels generated from an increase in IGF-binding protein (IGFBP) protease activity could be the inhibitory mechanism for the decreased growth hormone (GH) secretion observed in obese subjects.
Research Methods and Procedures: In this study, we determined basal and 24-hour levels of free IGF-I and -II, total IGF-I and -II, IGFBP-1, as well as basal IGFBP-2, −3, and −4, acid-labile subunit (ALS), IGFBP-1, −2, and −3 protease activity, and 24-hour GH release in obese women before and after a diet-induced weight loss. Sixteen obese women (age, 29.5 ± 1.4 years) participated in a weight loss program and 16 age-matched non-obese women served as controls.
Results: Circulating free IGF-I and 24-hour GH release were significantly decreased in obese women at before weight loss compared with non-obese women (1.29 ± 0.12 vs. 0.60 ± 0.09 μg/L; p < 0.001 and 862 ± 90 vs. 404 ± 77 mU/24 hours; p < 0.001, respectively). Free IGF-I and 24-hour GH release were not inversely correlated to each other. IGFBP-1 and −2 levels were decreased, whereas ALS, IGFBP-3 and −4, and IGFBP-1, −2, and −3 protease activity were similar in obese and non-obese women. Eight of the 16 obese women achieved an average weight loss of 30 ± 5 kg during 26 to 60 weeks of dieting. After the considerable weight loss, significant differences in free IGF-I, GH release, and IGFBP-1 and −2 levels were no longer present between previously obese and non-obese women.
Discussion: We showed that circulating free IGF-I is markedly decreased in severely obese women and does not per se mediate the concomitant hyposomatotropism. The decreased levels of free IGF-I seem to be transient and restored to normal levels after weight loss.