BMI has been shown to be inversely associated with testosterone levels. The Swedish MrOS study, which included an analysis of 2416 men, showed a statistically significant decrease in BMI with increasing quartiles of total testosterone. (A quartile is a range of data values of three points that divide the data range into four equal groups, each group comprising a quarter of the data).
The average BMI of the subjects in the fourth (upper hormone range) quartile of total testosterone was 24.9, compared with 28.1 for those subjects in the first (lower hormone range) quartile of total testosterone. A similar inverse association between total testosterone levels and BMI was observed in the large population-based Hypogonadism In Males study as well. The Hypogonadism In Males study compared 836 hypogonadal men with 1326 eugonadal men. The mean BMI for hypogonadal men was found to be 31.5 compared with 28.5 for eugonadal men. The authors also demonstrated that the odds ratio for having hypogonadism was significantly higher in obese men, and there was a statistically significant negative correlation between total testosterone level and BMI.
The effects of testosterone replacement therapy on BMI were investigated by Kalinchenko et al. in 113 men with metabolic syndrome, who received a total of 3 intramuscular injections of testosterone—at baseline and after 6 and 18 weeks. Patients receiving testosterone replacement therapy were shown to have statistically significant improvement in their BMI, which had decreased by 1.3 at 30 weeks. Testosterone replacement therapy has also been shown to decrease fat mass. Corona et al. demonstrated in their meta-analysis that testosterone replacement therapy resulted in a decrease of 2.19% in fat mass. This discovery was confirmed in animal models as well.
The exact mechanism of action through which testosterone and obesity interact is unknown. This interaction may be a result of the promotion of lipolysis in abdominal adipose tissue by testosterone, which may, in turn, cause reduced abdominal adiposity. On the other hand, given that adipose tissue has a higher concentration of the enzyme aromatase, it could be that increased adipose tissue results in more testosterone being converted to estrogen, thereby causing hypogonadism. Third, increased abdominal obesity may cause reduced testosterone secretion by negatively affecting the hypothalamus-pituitary-testicular axis. Finally, testosterone may be the key factor in activating the enzyme 11-hydroxysteroid dehydrogenase in adipose tissue, which transforms glucocorticoids into their inactive form.
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Ohlsson C, Barrett-Connor E, Bhasin S, Orwoll E, Labrie F, Karlsson M, Ljunggren O, Vandenput L, Mellstrom D, Tivesten A. High serum testosterone is associated with reduced risk of cardiovascular events in elderly men. The MrOS (Osteoporotic fractures in men) study in Sweden. J Am Coll Cardiology.2011; 58:1674-1682.
Mulligan T, Frick MF, Zuraw QC, Stemhagen A, McWhirter C. Prevalence of hypogonadism in males aged at least 45 years: the HIM study. Int J Clin Pract.2006; 60:762-769.
Kalinchenko SY, Tishova YA, Mskhalaya GJ, Gooren LJG, Giltay EJ, Saad F. Effects of testosterone supplementation on markers of the metabolic syndrome and inflammation in hypogonadal men with the metabolic syndrome: the double-blinded placebo-controlled Moscow study. Clin Endocrinol. 2010; 73:602-612.
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