SERUM LEVELS OF TYPE-I PROCOLLAGEN C-TERMINAL PROPEPTIDE, INSULIN-LIKE GROWTH-FACTOR-I (IGF-I), AND IGF BINDING PROTEIN-3 IN OBESE CHILDRENAND ADOLESCENTS - RELATIONSHIP TO GENDER PUBERTAL DEVELOPMENT, GROWTH, INSULIN, AND NUTRITIONAL-STATUS

We measured fasting serum revels of type I procollagen C-terminal prop eptide (PICP), insulin-like growth factor-I (IGF-I), and IGF binding p rotein-3 (IGFBP-3) in obese children and adolescents (obese subjects [ OS]) to evaluate their relationship to growth, gender, pubertal stage, and weight excess (WE). The influence of insulin, growth hormone (GH) , and weight loss was also studied. The study population consisted of 244 OS and 236 normal-weight subjects (NWS) matched for age, gender, a nd pubertal stage. At stage I, OS had a higher standard deviation scor e (SDS) for height than NWS of both genders. During the prepubertal ph ase, growth velocity (GV) was greater in OS than in NWS of both gender s, but it was lower in female OS at stage II and male OS at stage III. PICP increased in puberty, with a more rapid decrease later in female OS and NWS; prepubertal values were higher in OS but were reduced at pubertal stage IV to V in comparison to NWS. Stepwise multiple regress ion analysis demonstrated that GV was the only anthropological variabl e correlating with PICP. IGF-I serum values increased significantly in puberty and were higher in OS than in NWS at stage I for both genders . IGFBP-3 values of OS exceeded those of NWS at stages I to III in mal es and I to Il in females. No difference was observed for males versus females in each group, nor was any difference observed for the IGF-I/ IGFBP-3 molar ratio between the two groups. Using stepwise analysis, a positive correlation between IGF-I and IGFBP-3 was observed in prepub ertal but not. in pubertal NWS. Easting insulin values correlated with IGFBP-3 in OS, accounting far 24.8% of the variation in prepubertal s ubjects and 17.1% in pubertal subjects. No such correlation was observ ed in NWS. In prepubertal NWS, PICP and SDS of body mass index (BMI) c orrelated with IGF-I, accounting for 12.9% of the variation, and SDS o f BMI correlated with IGFBP-3, explaining 27.8% of the variation. In p repubertal OS, no such correlations could be observed, but PICP and SD S of BMI accounted for 14.3% of the variation in the IGF-I/IGFBP-3 mol ar ratio. A significant reduction of IGFBP-3 and an increase of the IG F-I/IGFBP-3 molar ratio were detected after weight loss in 40 OS. In c onclusion, we demonstrated that IGF-I and IGFBP-3 are influenced by ag e, gender, sexual development, and nutritional status. Also, an influe nce of insulin on IGFBP-3 serum levels was observed in OS. The relatio ns of IGF-I to PICP in NWS and of the IGF-I/IGFBP-3 molar patio to PIC P in OS support the concept of IGF-I influence on skeletal growth. The increased IGFBP-3 serum values in OS suggest a possible role in contr olling the growth stimulus induced by nutritional status. Copyright (C ) 1997 by W.B. Saunders Company.