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Circulating concentrations of leptin (leptin) vary directly with body mass index and percentage body fat, and may thus constitute an afferent limb of a system regulating body fatness. We tested the hypotheses that: 1) Plasma leptin vary more directly with absolute fat mass than with fractional body fatness per se: and 2). The relationship between fat mass and leptin is significantly affected by gender and by menopausal status. Leptin in the post-absorptive state was examined in 67 subjects (26 male, 20 premenopausal female, 21 postmenopausal females; 43 never-obese, 24 obese) at usual body weight. Body composition was determined by hydrodensitometry, and leptin was determined by a double antibody ELISA assay. In male and pre-menopausal female subjects, subcutaneous adipose tissue aspirations were performed for determination of adipocyte volume by the osmium fixation method, and a 3 hour oral glucose tolerance tests was performed. At usual body weight, (leptin) was better correlated with absolute fat mass than with body mass index (BMI) or percentage body fat. BMI and % body fat did not account for any of the variance in leptin beyond that attributable to FM, per se. The regression equations relating FM to leptin did not differ significantly between obese and never-obese subjects. Leptin and fasting serum insulin concentrations were significantly correlated in males only. Leptin was significantly higher in pre- and post-menopausal females compared to males, even when leptin was corrected for differences in body composition (pre-menopausal females > post-menopausal females > males). While plasma leptin, corrected for FM, declines significantly in women post-menopause, this decline is not sufficient to account for the striking sexual dimorphism in the relationship of leptin to fat mass. This sexual dimorphism is apparently also due, in part, to a suppressive effect of circulating androgens on leptin.
Rosenbaum et al. (Sun,) studied this question.