Association of age and insulin resistance with sex hormone-binding globulin levels in healthy men

To evaluate the putative association of age and insulin resistance with sex hormone-binding globulin levels in healthy men. In total, 136 healthy men without obesity, aged 18 years or older, were included. Total testosterone was measured by electrochemiluminescence, and sex hormone-binding globulin by chemiluminescence. Calculated free testosterone was obtained by Vermeulen's equation. Insulin resistance index was estimated as triglycerides/HDL ratio. The sample was divided into tertiles according to age (18 to 29; 30 to 49; 50 to 67 years). Sex hormone-binding globulin levels were higher in men > 50 years old compared to those of the second and first tertiles (41 ± 17 versus 35 ± 12 and 29 ± 9 nmol/L; p < 0.001), while values of calculated free testosterone were lower in the older tertile (7.7 ± 1.9 versus 8.8 ± 2.2 and 10.4 ±3.1 ng/dL; p < 0.001). Age did not influence total testosterone levels. Insulin resistance index was inversely and significantly correlated with sex hormone-binding globulin (r = -0.371; p < 0.001). There is a significant increase in serum sex hormone-binding globulin in older healthy men, highlighting the need for age-specific reference values. Furthermore, insulin resistance seems to reduce this globulin levels, perhaps pointing out low sex hormone-binding globulin as a putative predictor of related chronic diseases.