CORRELATIONS BETWEEN BONE-MINERAL DENSITY, INSULIN-LIKE GROWTH-FACTOR-I AND AUXOLOGICAL VARIABLES

Recent studies have shown growth-related changes in spinal bone minera l density (BMD) in children; however, there is less information availa ble on the relationship between BMD and insulin-like growth factor I ( IGF-I). The aim of this study was to relate the BMD of the spine and r adius with serum IGF-I levels and auxological variables in normally gr owing children. We used dual X-ray absorptiometry to measure the BMD i n the lumbar spine (L1-L4) and distal radius of 121 children (69 boys, 52 girls) aged 3-18 years whose growth velocity was normal. Lumbar an d radial BMD increased with age (p < 0.001) and puberty (p < 0.001) an d was highly correlated to age, weight, height, body surface and bone agr (r = 0.70-0.89 and p < 0.001 for all variables). Partial correlati on, with age held constant, was weaker but still significant for most auxological variables. Serum IGF-I concentrations increased slowly dur ing childhood and markedly during early stages of puberty, and correla ted with lumbar and radial BMD (r = 0.55 and 0.45, respectively; p < 0 .001) and with the auxological variables and with BMD, except in the c ase of radial BMD in boys. By multiple regression analysis IGF-I, unli ke auxological variables, did not reach significance in the ability to predict BMD. Therefore, in healthy children, serum IGF-I levels show a weaker relationship in BMD than do auxological variables.