Effect of cigarette smoking on levels of bioavailable testosterone in healthy men

Abstract

The effect of smoking on androgen levels is important given the recent interest in the link between low levels of androgens and the development of cardiovascular disease. Numerous studies examining the effects of cigarette smoking on the levels of total and free testosterone have reported conflicting findings, but there has been no accurate assessment of the effects of cigarette smoking on the levels of bioavailable testosterone [not bound to sex hormone-binding globulin (SHBG)]. We attempted to determine whether smoking affects the level of bioavailable testosterone. We undertook a case-control study of 25 healthy male smokers and 25 healthy never-smokers, matched by age and body mass index. Early morning levels of total, free and bioavailable testosterone, 17beta-oestradiol, SHBG and cotinine were determined and compared between the two groups. Levels of total (18.5+/-4.6 nM versus 15.1+/-4.9 nM, P=0.01) and free testosterone (462+/-91 pM versus 402+/-93 pM, P=0.03) were found to be higher in smokers compared with non-smokers respectively, as was SHBG (34.1+/-12.8 versus 28.1+/-9.0 nM, P=0.06). There were no significant differences in the levels of bioavailable testosterone (3.78+/-1.59 versus 3.51+/-1.26 nM, P=0.49) or 17beta-oestradiol (44.5+/-11.4 versus 42.3+/-11.5 pM, P=0.50) between smokers and non-smokers respectively. These data suggest that cigarette smoking has no significant effect on the biologically active fraction of testosterone, but may influence the levels of total and free testosterone through changes in the levels of SHBG.

The Inverse Relationship Between Thoracic Aortic Intima Media Thickness and Testosterone Level

“…Similarly, we found that testosterone showed inverse correlations with fibrinogen, HsCRP, uric acid, white blood cell, and smoking. The results of previous studies describing the effects of cigarette smoking on testosterone levels in human males have been conflicting, and no significant effect on the biologically active fraction of testosterone has been shown, but smoking may influence the levels of total and free testosterone through changes in the levels of sex hormones binding globulin (27). The main difference between these findings and our findings may be related to the selection and characteristics of the patient population.…”

Reduced pulmonary function is associated with lower levels of endogenous total and free testosterone. The Tromsø Study

“…Although, some authors have reported lower [18] or similar [19] testosterone levels in healthy male smokers compared to non-smokers, most authors have found higher levels of total and free testosterone [10][11][12]. As SHBG levels also are increased in smoking men, it has been suggested that the increase in testosterone levels is a consequence of the increased SHBG levels.…”

“…Furthermore, testosterone supplementation has been found to improve lean body mass and body composition in men with COPD [7][8][9]. It is generally agreed that smoking is strongly associated with reduction in pulmonary function, and in several cross-sectional studies smoking has been associated with higher both total and free testosterone levels [10][11][12]. Thus, there are several strong and interesting relationships between testosterone levels and pulmonary functions, but to our knowledge no large population-based study has investigated these associations.…”

Higher serum testosterone and dihydrotestosterone, but not oestradiol, are independently associated with favourable indices of lung function in community‐dwelling men

“…Several studies have explored this relationship, reporting higher T concentrations in current smokers [13][14][15]. The mechanism is unclear but it has been postulated that smoking may have a centrally mediated effect on the axis, or may act indirectly by increasing SHBG concentrations, thereby increasing circulating T [13][14][15]. Smoking itself is a powerful risk factor for respiratory ill-health including from chronic obstructive pulmonary disease (COPD) and lung cancer [16].…”