Leptin plasma levels in the general population: influence of age, gender, body weight and medical history.

The polypeptide leptin exerts a multitude of regulatory functions. It has been implicated in the pathophysiology of inflammatory, metabolic and psychiatric disorders and has been found to be differentially expressed in men and women. Although a clear increase of leptin levels with age has been repeatedly observed in men, the association of leptin levels and age in women is an issue of scientific discussion. To investigate the association of age, gender, body mass index (BMI) and selected diseases with plasma levels of leptin in 551 adults randomly chosen from the Bavarian population, we assessed subjects' characteristics, lifestyle, and medical history including life time history of frequent diseases and performed blood sampling and standardized anthropometric measurements. Leptin plasma levels were measured using a Radioimmunoassay. Leptin levels were significantly higher in women as compared to men and this difference persisted even after controlling for differences in age or BMI. Leptin levels increased across the age groups in both men and women. Controlling for differences in BMI substantially attenuated the influence of age on leptin levels. In women, age was no longer significantly associated with leptin levels after controlling for BMI. With regard to medical history, hyperuricemia and gout were significantly associated with higher leptin levels, even after controlling for BMI, whereas subjects with high blood pressure or dyslipoproteinemia showed higher leptin levels only if the BMI was not considered as control variable. The BMI and its influence on the interrelations of gender, age and leptin should be considered when interpreting leptin levels.