Leptin in the General Population, Differences in Sex Hormones, Blood Lipids, Gender and Life Style Characteristics

Introduction: Fat mass is the main predictor of the serum concentration of leptin, a 167-amino acid peptide hormone encoded by the obesity gene. There is no general agreement about other determinant factors of serum leptin, but attention has been focused on gender and sex hormones. The objective of this study was to describe gender differences in a population study and evaluate the individual contribution of life style characteristics, blood lipid pattern and sex hormones as determinants of serum leptin. Materials and Methodology: In a multipurpose, cross-sectional general health survey, ("Tromso IV"- N = 27.159), conducted during the years 1994/95, measurement of leptin was performed in a sub sample of 1812 subjects. Multiple regression analysis was performed in order to establish the importance of each predictor. Results: Gender differences in leptin increased with increasing BMI, and the gender predicted 33 % of the variation of leptin. Differences in life style factors between men and women could not explain gender differences. Smoking, physical activity, testosterone and SHBG were independent negative predictive factors. Estradiol was positive predictive factor of serum leptin. However, all contributed to a small variation in serum leptin. A gender dimorphism was observed between serum leptin and serum testosterone and between serum testosterone and BMI. Conclusions: BMI and gender were strong predictors in variations in serum leptin. Life style factors and sex hormones were less predictive. Gender dimorphisms between leptin, testosterone and BMI indicate a complex relationship between body fat distribution and the two hormones.