A. Falorni et al., 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, Metabolism, clinical and experimental, 46(8), 1997, pp. 862-871
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.