ABSTRACT
<p><b>OBJECTIVE</b>To 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.</p><p><b>METHODS</b>The 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.</p><p><b>RESULTS</b>Serum 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.</p><p><b>CONCLUSIONS</b>Serum 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.</p>