The metabolic syndrome and insulin-like growth factor I regulation in adolescent obesity

J Clin Endocrinol Metab. 1998 May;83(5):1467-71. doi: 10.1210/jcem.83.5.4827.

Abstract

Although low GH levels are commonly seen in obese adults and children, the effects of obesity on the insulin-like growth factor (IGF)/IGF-binding protein (IGFBP) system have not been established. As GH and IGF-I normally increase during adolescence, we investigated the effects of obesity on circulating total and free IGF-I levels and IGFBP-1, -2, and -3 in 19 obese adolescents [14 +/- 1 yr old; body mass index (BMI), 34 +/- 3], 20 lean adolescents (14 +/- 1 yr old; BMI, 23 +/- 0.5), and 10 lean adults (22 +/- 0.7 yr; BMI, 22 +/- 0.7). Fasting plasma insulin levels were significantly greater in obese adolescents than in either lean group, whereas circulating IGFBP-1 levels were suppressed in an inverse relationship to basal insulin (r = -0.49; P < 0.01). Low IGFBP-1 levels were associated with normal to increased free IGF-I levels in obese adolescents, even though total IGF-I values were lower than those in lean adolescents. Basal GH and IGFBP-3 levels were also lower in obese vs. lean adolescents. Basal IGFBP-1 levels were markedly reduced in obese adolescents (14 +/- 3 ng/mL) vs. those in adolescents and adults. No further suppression of IGFBP-1 levels was observed in the obese group during a two-step 8 and 40 mU/m2 insulin clamp. In contrast, IGFBP-1 levels were promptly lowered in lean adults. Basal IGFBP-2 levels were significantly lower in both groups of adolescents vs. lean adults (P < 0.05), and IGFBP-2 levels did not change during euglycemic hyperinsulinemia. These data suggest that the compensatory hyperinsulinemia that characterizes adolescent obesity chronically suppresses levels of IGFBP-1, and low IGFBP-1 concentrations may serve to increase the bioavailability of free IGF-I, which may, in turn, contribute to lower circulating GH, total IGF-I, and IGFBP-3 concentrations.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Blood Glucose / metabolism
  • Body Mass Index
  • Child
  • Female
  • Glucose Clamp Technique
  • Homeostasis*
  • Humans
  • Insulin / blood
  • Insulin-Like Growth Factor Binding Protein 1 / blood
  • Insulin-Like Growth Factor Binding Protein 2 / blood
  • Insulin-Like Growth Factor Binding Protein 3 / blood
  • Insulin-Like Growth Factor I / metabolism*
  • Male
  • Obesity / metabolism*

Substances

  • Blood Glucose
  • Insulin
  • Insulin-Like Growth Factor Binding Protein 1
  • Insulin-Like Growth Factor Binding Protein 2
  • Insulin-Like Growth Factor Binding Protein 3
  • Insulin-Like Growth Factor I