Sex-specific determinants of serum adiponectin in older adults: the role of endogenous sex hormones.

OBJECTIVE: To assess the sex-specific association of adiponectin with multiple factors thought to influence its levels, with a special emphasis on endogenous sex hormones. DESIGN AND METHODS: A cross-sectional study of determinants of serum adiponectin in 873 men and 673 postmenopausal women, ages 50-92. Factors evaluated include age, body size, fat distribution, lifestyle (exercise, smoking, alcohol intake), insulin resistance, renal function and endogenous sex hormone levels (total and bioavailable testosterone and estradiol).
RESULTS: Median serum adiponectin was 50% higher in women than men (P<0.001). In unadjusted analyses, adiponectin was positively related to age, alcohol intake, high-density lipoprotein (HDL) and testosterone, and negatively related to waist girth, body mass index, Homeostasis Model Assessment for Insulin Resistance (HOMA-IR), triglycerides and bioavailable estradiol in both sexes (all P<0.01). Adiponectin was positively related to blood urea nitrogen, a measure of renal function, in men only (P<0.001). Sex-specific multivariate linear regressions adjusting for HDL and triglycerides showed that only age, HOMA-IR and sex hormones independently predicted circulating adiponectin for both men and women. Higher levels of endogenous testosterone and lower bioavailable estradiol concentrations each predicted higher adiponectin; this was true for both sexes, and was not explained by differences in age, adiposity, alcohol intake, insulin resistance or lipoprotein levels.
CONCLUSIONS: The association of adiponectin with the factors studied here is strikingly similar for men and women. Sex differences in circulating adiponectin levels in older adults cannot be explained by sex hormone regulation.