Serum markers of GH and insulin action in 12-year-old children born small for gestational age.

OBJECTIVES: Our aim was to determine whether markers of growth hormone and insulin action differ between children born small for gestational age (SGA) and those born of an appropriate size for gestational age (AGA).

DESIGN: Fifty-five SGA children and their 55 age- and sex-matched AGA control subjects were studied in a case-control setting at 12 years of age.

METHODS: We examined serum concentrations of insulin-like growth factor (IGF)-I, IGF-II, IGF-binding protein (IGFBP)-1 and IGFBP-3, sex hormone binding globulin (SHBG), leptin, fasting insulin, and blood glucose. Insulin sensitivity was evaluated by the homeostasis model assessment for insulin resistance (HOMA-IR).

RESULTS: The body mass index (BMI), sex, and puberty-adjusted mean serum IGF-I concentration was higher in the SGA than in the AGA children (303.4 vs 282.3 microg/l, P = 0.006). The mean serum concentrations of IGF-II, IGFBP-I, IGFBP-3, SHBG, fasting insulin, blood glucose and HOMA-IR did not differ between the SGA and the AGA group. The BMI, sex, and puberty-adjusted mean serum leptin concentration was lower in the SGA than in the AGA children (7.9 vs 10.1 microg/l, P = 0.037). In multiple logistic regression analysis, high HOMA-IR predicted high serum IGF-I levels in the SGA children (odds ratio 8.3; 95% confidence interval 1.7-41; P = 0.010), whereas in the AGA group HOMA-IR did not associate with the serum IGF-I level.

CONCLUSIONS: The BMI, sex, and puberty-adjusted mean serum IGF-I concentration was significantly higher and the leptin concentration was lower in the SGA than in the AGA children. No differences were found in the indices of insulin action or sensitivity between the SGA and AGA children at 12 years of age. However, HOMA-IR strongly associated with serum IGF-I levels in the SGA children.