Serum leptin concentration in Tunisian non obese children.

Leptin, an adipocyte-derived peptide hormone, is thought to play a key role in the regulation of body fat mass. Beyond this function, it appears to be an integral component of various hypothalamo-pituitary-endocrine feedback loops. Because childhood and puberty are periods of major metabolic and endocrine changes, we investigated leptin levels in 348 non overweight, non obese children (147 boys, 201 girls, age: 6-12 years) and then correlated these levels with age, anthropometric data, pubertal stage and insulin. A blood sample was collected from each subject to measure leptin and insulin levels by radioimmunoassay. Pubertal stage was assigned by physical examination, according to Tanner criteria for breast development in females and genital development in males. The results showed an increase in leptin levels in an age related way (r = 0.32, p < 0.0001 in girls; r = 0.21, p = 0.011 in boys) following a pattern that paralleled body weight (r = 0.6 in girls; r = 0.56 in boys; p < 0.0001) and BMI (r = 0.59 in girls; r = 0.6 in boys, p < 0.0001), suggesting that body fatness is a regulator of leptin levels in both girls and boys. A significant gender difference (3.39 +/- 2.79 ng/mL in girls vs 1.99 +/- 2.08 ng/mL in boys, p < 0.0001) with an increase during pubertal development in girls was also showed, while the levels remained constant in boys from Tanner stages T1 to T3. A correlation between leptin and insulinemia was noted in girls (r = 0.38, p < 0.0001) but not in boys, suggesting that insulinemia could be a stimulator of leptin synthesis in girls.