SHBG and Insulin resistance: Obese men have lower serum testosterone concentrations than non-obese men (22), due to modifications in sex hormone binding globulin (SHBG), increase in the aromatase enzyme activity of adipocytes (23, 24), low-grade systemic inflammation, increase in oestradiol concentrations, hyperinsulinemia/insulin resistance, and hyperleptinemia/lleptin resistance (22–24) (Figure 1).