Serum leptin levels in healthy ageing men: are decreased serum testosterone and increased adiposity in elderly men the consequence of leptin deficiency?

OBJECTIVE The limited information on serum leptin levels in elderly men sug gests the occurrence of an age-related decrease, with disruption of the rel ationship between fat mass and leptin levels. A relative leptin deficiency might thus be implicated in the increase of fat mass and decrease of serum testosterone levels in elderly men. Therefore, we have reevaluated the age- related changes in serum leptin levels and their relationship with adiposit y and androgen levels in a large group of community dwelling men. SUBJECTS AND MEASUREMENTS Serum leptin and androgen levels were measured in 271 healthy, ambulatory elderly men (median age 74 years), as well as in 6 1 middle-aged (median 43years) and 40 young (median 25.5 years) controls. A diposity was assessed by anthropometrical measurements (body mass index; BM I) and by estimation of fat mass by the bioimpedance method. RESULTS Serum leptin levels, whether or not adjusted for BMI, were found to increase with age, the values tending to level off after the age of 45 yea rs, and were strongly correlated to BMI (r = 0.77) and fat mass assessed by the bio-impedance method (r = 0.81). Linear regression analysis showed a s imilar slope for the relationship between BMI and serum leptin in the three age groups. Multiple linear regression analysis indicated BMI, age and ser um insulin, but not serum testosterone, as significant independent correlat es of serum leptin, Serum (free) testosterone levels were negatively correl ated with age and serum leptin, also after partialization for BMI: rank cor relation coefficients vs. age and serum leptin, respectively, were -0.20 (P <0.001) and -0.16 (P<0.01) for total testosterone and -0.60 (P<0.001) and - 0.23 (P<0.001) for free testosterone. Dehydroepiandrosterone sulphate (DHE AS) and leptin levels emerged as significant independent correlates in a mu ltiple linear regression model for total serum testosterone; BWI and serum insulin became highly significant correlates in the same model when leptin was omitted from the independent variables. CONCLUSION Ageing in men is accompanied by a rise of serum leptin levels wi th a maintained strong association between serum leptin and adiposity in el derly men. Testosterone does not appear to be a major determinant of serum leptin in healthy men, while leptin does emerge as a negative correlate of serum testosterone, Increased fat mass and decreased testosterone productio n in elderly men cannot be attributed to a relative leptin deficiency.