Objective: To investigate the levels and diurnal rhythm of serum leptin in healthy children, and to investigate the association between leptin levels and sex steroids. Methods: Four girls and four boys, all healthy volunteers, were followed longitudinally throughout puberty. Their chronological ages ranged from 8.7 to 19.5 years, and body composition, expressed as weight-for-height standard deviation scores (SDS), ranged between 21.7 and +2.4. Serum leptin, oestradiol and testosterone

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... ions were measured by radioimmunoassay at 1000, 1400, 1800, 2200, 0200 and 0600 h. Results: In all girls and boys, both prepubertally and during pubertal development, serum leptin levels increased during the night, with no difference in relative peak amplitude. In boys, the leptin concentrations increased until the initiation of puberty and then declined, whereas in girls, the concentrations increased throughout puberty. The inter-individual variation in mean leptin levels among girls decreased to 11% at the time of menarche. A positive correlation was found for both oestradiol and testosterone versus leptin in girls throughout puberty r 0X64 and r 0X71 respectively, P , 0X001X A negative correlation was found between leptin and testosterone in boys in mid-and late puberty r 20X66Y P , 0X01X No correlation was found between oestradiol and leptin in boys or between testosterone and leptin in pre-and early pubertal boys. Conclusion: Serum leptin concentrations show diurnal variation throughout pubertal development in both girls and boys. The changes in leptin levels during puberty follow a gender-specific pattern, probably due to an influence of sex steroids on leptin production.