Plasma Free and Non-Sex-Hormone-Binding-Globulin Bound Testosterone Are Decreased in Obese Men in Proportion to Their Degree of Obesity

Abstract

It is known that plasma total testosterone (T) is decreased in obese men in proportion to the degree of obesity, but similar information is not available for plasma free T and non-sex-hormone-binding globulin (SHBG)-bound T. We measured the 24-h mean plasma total T in 48 healthy (non-weight-stable men, aged 18-55 yr, with body mass indexes (BMI) ranging from 21-95 kg/m2. Free T and non-SHBG-bound T were calculated using the measured total T, the concentrations of albumin and SHBG, and the association constants of T to albumin and SHBG. Total body fat content was measured by deuterium-water isotope dilution. Findings were as follows. 1) BMI was very highly correlated with total body fat content (r = 0.96; P less than 0.001); thus, the degree of obesity can be calculated just as appropriately from simple height and weight measurements as from measurements of total body fat content. 2) Total, non-SHBG-bound, and free T were all highly correlated inversely with BMI; for total T, r = -0.727, P less than 0.01; for non-SHBG-bound T, r = 0.677, P less than 0.01; and for free T, r = -0.653, P less than 0.01. Thus, free T and non-SHBG-bound T are decreased in obese men in proportion to the degree of obesity, just as is the case for total T; percentage-wise, the decrease was the same for all 3 parameters.

A strong association between biologically active testosterone and leptin in non-obese men and women is lost with increasing (central) adiposity

“…39 It is notable that measures of biologically active testosterone (FT and NST) associate with leptin in a nearly identical pattern in both men and women, supporting the view that free and albumin-bound testosterone fractions have the same biological role. 45 In contrast, the pattern of associations between leptin and TT, which includes non-biologically active testosterone bound to SHBG, resembles both the associations between biologically active testosterone and leptin, and the association between SHBG and leptin, especially in men. These different patterns should be taken into consideration when evaluating earlier reports.…”

Severity of erectile dysfunction in married impotent patients: Interrelationship with anthropometry, hormones, metabolic profiles and lifestyle

“…In obese men, lower levels of serum total testosterone and serum free testosterone were found. 25 It has been shown that aromatization of testosterone to estradiol is increased in obese older men 26 and possible links to ED were speculated. In addition, obesity and the MS are states of chronic oxidative stress and inflammation, which may increase free radical formation which could quench and deactivate nitric oxide, reducing its availability for target cells.…”

Pubertal development in obese children and adolescents

“…In male adults, low total testosterone levels are frequently found in obesity together with low SHBG levels as well as decreased free testosterone levels. 46,47 In some cases, an association with a reduced sperm count was found. 48 A recent study even showed lower fertility in obese men with a dose relationship to BMI.…”