Hormone Replacement Therapy and Interrelation between Serum Interleukin-6 and Body Mass Index in Postmenopausal Women: A Population-Based Study

Postmenopausal women are at increased risk to develop osteoporosis, coronary artery disease, heart failure, and hypertension. Interleukin-6 (IL-6) may be a pathogenetic element in these disorders. Serum IL-6 levels increase during aging and seem to be related to increased body fat mass. In the present retrospective study we aimed to investigate the role of hormone replacement therapy (HRT) on serum IL-6 levels and the interrelation of IL-6 and body fat mass. Parameters were assessed in a population-based sample of postmenopausal women (n = 302) and, for comparison, 245 men of the same age. Women with HRT (n = 92) had significantly lower serum IL-6 levels compared to subjects without HRT, which was independent of age, antihypertensive therapy, smoking habits, and blood pressure (1.5 +/- 0.1 vs. 2.9 +/- 0.6 pg/mL; P = 0.017). In women without HRT, the body mass index (BMI) was correlated with serum IL-6 levels (P < 0.001). Multivariate analysis controlling simultaneously for the effects of blood pressure and heart rate confirmed the positive correlation (P = 0.001). However, in subjects with HRT no such correlation between IL-6 and BMI was demonstrated, which was confirmed after controlling covariates. In male subjects, BMI correlated with serum IL-6 (P = 0.009), which was, however, blunted after controlling for blood pressure and heart rate, probably indicating an influence of the sympathetic nervous system on this interrelation. In conclusion, women receiving HRT display lower serum IL-6 levels and a blunted interrelation of IL-6 and BMI. As IL-6 may be a pathogenetic factor in age-related diseases, HRT-related inhibition of IL-6 secretion could be an important element for the favorable effects of HRT in postmenopausal women.