INSULIN-LIKE-GROWTH-FACTOR BINDING PROTEIN-I LEVELS ARE STRONGLY ASSOCIATED WITH INSULIN SENSITIVITY AND OBESITY IN EARLY PUBERTAL CHILDREN

In conditions associated with insulin resistance, insulin-like growth factor binding protein-I (IGFBP-I) levels have been shown to correlate inversely with insulin levels. Puberty is associated with insulin res istance and thus provides a model for comparing the relationship of IG FBP-I to both insulin levels and measures of insulin sensitivity. Our study population consisted of 104 healthy pubertal children, age 9.8-1 4.6 yr. Each subject had his/her insulin sensitivity (Si) assessed by the modified minimal model of Bergman, which employs a frequently samp led iv glucose tolerance test. Results showed that IGFBP-I levels were significantly higher in boys than in pubertally matched girls (P < 0. 01). There was a strong positive correlation between IGFBP-I levels an d Si (r = 0.65, P < 0.0001) and a weaker negative correlation with fas ting insulin levels (r = -0.38, P < 0.0001). An inverse relationship w as also found between IGFBP-I levels and body mass index (r = -0.46, P < 0.0001) and with IGF-I levels (girls only, r = -0.41, P < 0.003). C onsequently, insulin sensitivity, obesity, and IGF-I are important pre dictors of IGFBP-I levels in pubertal children. It is possible that in sulin-mediated suppression of IGFBP-I in obese children may increase f ree IGF-I levels and thus contribute to somatic growth. The same mecha nism may operate in pubertal children, where insulin resistance and gr owth acceleration occur simultaneously.