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Does nicotine lower testosterone?

Consistent with the hypothesis that cotinine, a metabolite of nicotine in cigarettes, may competitively inhibit androgen breakdown, and thus increase androgens, smoking was associated with higher testosterone among men and possibly women.

sciencedirect.com - Cigarette smoking and testosterone in men and women - ScienceDirect.com

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What age do men have highest testosterone?

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Cardiovascular disease (CVD) is the leading cause of mortality globally (Lozano et al., 2013), with men having higher age-specific mortality rates than women (Kalin and Zumoff, 1990). Observationally serum testosterone is associated with lower cardiovascular disease (CVD) morbidity/mortality (Ruige et al., 2011). However, observational studies providing associations concerning endogenous testosterone are open to reverse causality because serum testosterone falls with age and ill-health (Feldman, HA, et al., 2002, Shi, Z, et al., 2013). Meta-analyses of small randomized controlled trials (RCTs) have not confirmed benefits of testosterone therapy among men, but suggested effects in the other direction (Xu, L, et al., 2013, Fernandez-Balsells, MM, et al., 2010). Endogenous and exogenous testosterone may have different roles. However, Mendelian randomization studies, using genetically determined serum testosterone, have also shown no benefits of endogenous testosterone for CVD risk factors (Zhao, J, et al., 2014, Haring, R, et al., 2013). The Food and Drug Administration (FDA) in the US and Health Canada have recently highlighted the possible cardiovascular risk of testosterone as a cause of heart attack (Health Canada, 2015, FDA, 2015a), stroke (Health Canada, 2015, FDA, 2015a), blood clots (Health Canada, 2015, FDA, 2015b) and venous thromboembolism (FDA, 2015-b). As such, environmental drivers of androgens could provide mechanistic insight and new prevention strategies for CVD. Smoking is a well-established cause of CVD, although the mechanism by which smoking causes such a wide range of diseases has not been fully elucidated (Carter et al., 2015). Smoking would also be expected to increase testosterone because nicotine and/or its metabolites share a disposal pathway with androgens, and so could competitively inhibit androgen disposal (Schooling, 2015). Specifically, testosterone, cotinine and trans-3′-hydroxycotinine (3HC) are all inactivated by glucuronidation, i.e., conjugation by enzymes from the uridine 5′-diphospho (UDP)-glucuronosyltransferase (UGT) superfamily (Chen, G, et al., 2010, Chouinard, S, et al., 2008), with the same UGT enzyme used for glucuronidation of both nicotine metabolites and androgens: the UGT2B10 enzyme for nicotine and cotinine, the UGT2B17 enzyme for 3HC (Chen et al., 2010), and the UGT2B7, UGT2B15 and UGT2B17 enzymes for androgens (Chouinard et al., 2008). Consistent with this potential mechanism (Schooling, 2015), some studies have reported higher androgens in smokers (Field et al., 1994). Commonality also exists between some effects of smoking and of androgens. For example, smoking promotes thrombosis (Barua and Ambrose, 2013), lowers HDL-cholesterol (Chelland Campbell et al., 2008) and has pro-inflammatory effects (Barua and Ambrose, 2013). Similarly, androgens promote thromboxane (Ajayi et al., 1995), raise hematocrit, lower high-density lipoprotein (HDL)-cholesterol (Fernandez-Balsells et al., 2010) and may promote low-grade systemic inflammation, by suppressing the immune system (Grossman, 1985). Smoking is also associated with prostate cancer (Carter et al., 2015). This same mechanism would also be expected to raise testosterone in users of smokeless tobacco (Schooling, 2015), which is associated with prostate cancer (Lee and Hamling, 2009), nicotine replacement or e-cigarettes. Notably, e-cigarettes also emit low levels of nicotine into the atmosphere (Grana et al., 2014), potentially causing harm by the same mechanism to bystanders. Given the known harms of smoking, RCTs examining the effect of smoking on androgens are not available. Observational studies have reported various associations of smoking with androgens (Wang, W, et al., 2013, Brand, JS, et al., 2011, Shaarawy, M and Mahmoud, KZ, 1982, Soldin, OP, et al., 2011). To our knowledge, no systematic review or meta-analysis has synthesized the association of smoking with serum androgens. To test the hypothesis that smoking raises androgens (Schooling, 2015), we carried out a systematic review and meta-analysis of observational studies, among men and women, to examine the association of cigarette smoking with two different biomarkers of serum androgens (testosterone and androstanediol glucuronide (AAG)).

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sciencedirect.com - Cigarette smoking and testosterone in men and women - ScienceDirect.com

Why am I so bloated and gaining weight?

Some causes may be related to stress, alcohol consumption, or medications. Other causes can be a result of health conditions like hypothyroidism or...

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