Obesity is characterized by a reduction in serum total testosterone concentration (left panel) but a normal serum free testosterone concentration (right panel) due to decreased SHBG.
SHBG: sex hormone-binding globulin.
Data from Glass AR, Swerdloff RS, Bray GA, et al. Low serum testosterone and sex-hormone-binding-globulin in massively obese men. J Clin Endocrinol Metab 1977; 45:1211.
