Biochemical markers of growth in the male and female adolescents - abstract

ABSTRACT

The biochemical markers of growth, insulin-like growth factor-1 (IGF-1) and the carboxyterminal propeptide of the type 1 procollagen (PICP) have been related to anthropometric indicators of growth. We have demonstrated a relationship among plasma levels of IGF-1 and height (ht) for age and weight (wt) for age Z-scores in children 2-10 years. PICP has been associated with height (kit) velocity. We therefore looked at plasma levels of these indicators in adolscents expected to attain maximum growth velocity during the year boys ( n=20) 13-14 years old (mean age, 13.7 years) and girls ( n=18) 11-12 years old (mean age, 11.6 years). Ht, wt, mid-upper arm circumference (MUAC), triceps and subscapular skinfold thickness were measured at baseline, then every 3 months for a year. At each visit, a venous blood sample was taken for plasma determinations of IGF - 1 and PICP by radioimmunoassay (RIA). The girls were slightly above and the boys were slightly below the NCHS references for their age with the exception of the triceps skinfold. The observed mean ht and wt velocities among the boys were 5.5 cm/year and 5.3 kg/year and the girls, 5.3 cm/year and 4.9 kg/year. The mean plasma level of IGF -1 in the adolescents were double those in the 2 - 10 year old age group with the girls (41.02 nmol/ml 95 percent CI22.0, 60.0) higher than the boys (35.39 nmol/ml 95 percent CI15.4,55.39). The difference was statistically significant. The mean plasma levels of PICP were similar for boys, (399.63 ng/ml 95 percent CI59.83, 739.43) and for the girls (398.76 ng/ml 95 percent CI 114.36, 683.16). These values were slightly higher than those in the 2-10 year-old age group. These values of IGF-1 and PIUCP are comparable to those of other populations. Mean percent body fat (PBF) increased linearly during the year in the girls, was related to the their body mass index (BMI) and was significantly higher than that in the boys. There was no association between PBF and BMI in the boys. Unlike the 2-10 year-old age group, there were no consistent relationships demonstrated among the anthropometric and the biochemical markers of growth in adolscents. This may reflect the mixed levels of maturity and the influence of the pubertal hormones in this group of adolescents. (AU)