OBJECTIVETo explore the changes of serum leptin, soluble leptin receptor (SOB-R) concentrations and free leptin index (FLI) throughout the puberty in females, and estimate the effects of genetic and environmental factors on these indices.

METHODSThe population studied consists of 180 pairs of twins in 6 to 18 years old: 132 pairs of monozygotic twins and 48 pairs of dizygotic twins, who were all from Qingdao city, Shandong Province. Anthropometric and sexual characteristics were examined, fasting serum leptin and SOB-R contents were assayed by immunoradiometric assay and ELISA respectively.

RESULTSSerum leptin concentrations increased and SOB-R decreased throughout puberty (P < 0.05), brought out a sustained increase of FLI, especially in 7-9 and 12-14 years old (from 10.1 to 32.3 and 41.8 to 82.1 respectively); Leptin and FLI were positively, and SOB-R negatively correlated with morphological indices (correlation coefficients from 0.54 to 0.76, -0.23 to -0.42, respectively). Heritability of girl's serum leptin, SOB-R and FLI were 0.37, 0.84, 0.46 respectively.

CONCLUSIONSSerum free leptin index surge at 7-9 and 12-14 years old might be a predictor or trigger of the puberty onset and menarche, respectively; FLI might be determined by both genetic and environmental factors. Leptin should be substantially influenced by environment and reflect the fat mass of body compositions. SOB-R should be predominantly controlled by genetic factors yet. Genetic influence might be important in pubertal development and metabolic disorders.