Smoking Cessation's Effects on Male Hormonal Levels

This scientific paper investigates the effects of smoking cessation on hormonal levels in men, specifically focusing on steroid hormones like testosterone, DHEA, DHEAS, cortisol, and sex hormone-binding globulin (SHBG). The researchers aimed to determine if these hormonal levels could predict successful smoking cessation and to observe hormonal changes in men one year after quitting. While their findings indicated no significant predictive power of basal hormone levels for quitting success, they observed a statistically significant decrease in SHBG and an increase in BMI in men who successfully quit smoking after one year. The study suggests that the observed decrease in SHBG might be a direct result of smoking cessation, independent of BMI changes.

Briefing Document: Effects of Smoking Cessation on Hormonal Levels in Men​

Source: Hruškovičová, H., Dušková, M., Šimůnková, K., et al. (2013). Effects of Smoking Cessation on Hormonal Levels in Men. Physiological Research, 62(1), 67-73.

Date of Publication: November 22, 2012 (On-line)

Summary: This study investigated the effects of smoking cessation on various steroid hormone levels (testosterone, DHEA, DHEAS, cortisol, and SHBG) in male smokers. It aimed to identify potential hormonal predictors of successful cessation and observe hormonal changes after one year of abstinence. The findings suggest that while chronic smoking can alter hormonal homeostasis, the impact on the male reproductive system is generally considered insignificant in terms of hormonal levels. The most notable change observed after one year of smoking cessation was a significant decrease in Sex Hormone-Binding Globulin (SHBG) levels, which occurred independently of BMI changes. The study also confirmed a common finding of weight gain after smoking cessation but did not find that baseline hormone levels could predict success in quitting.

Key Themes and Important Findings:​

1. Chronic Smoking and Hormonal Homeostasis:

• Broad Impact: Chronic smoking is known to cause "imbalance in endocrine homeostasis and impairment of fertility in both sexes." It affects various endocrine glands, including the pituitary, thyroid, adrenal, testicular, and ovarian functions, as well as calcium metabolism and insulin effect.
• Male Reproductive System: While the male reproductive system is considered "more resilient" than the female's in the context of smoking's effects, negative shifts in spermiogram parameters are commonly described in male smokers. Studies also link smoking to erectile dysfunction.
• Conflicting Testosterone Data: The literature presents conflicting results regarding smoking's influence on steroid hormone levels, particularly testosterone.
• Increased Testosterone: Many studies indicate "elevated testosterone level in male smokers," often positively correlated with the number of cigarettes smoked. This increase is frequently accompanied by "elevated SHBG in smokers."
• Decreased Testosterone: Conversely, some studies have found "reduced testosterone levels" and changes in enzyme expression in key tissues for androgen production due to smoking.
• HPA Axis Activation: Smoking "activates hypothalamic-pituitary-adrenal axis (HPA), stimulates adrenocorticotropic hormone (ACTH) secretion and enhances ACTH effect on adrenal cortex which results in stimulation of cortisol production." This is linked to lower sensitivity of nicotine receptors in the CNS.
• DHEA Levels: DHEA levels can "increased after one cigarette smoked" and also in chronic smokers. DHEA is considered a potential antidepressant and has been suggested as a medication for smoking cessation, with its levels inversely correlating with negative effects and cigarette craving.

2. Effects of Smoking Cessation:

• Limited Data: Prior to this study, "The data about smoking cessation are limited; there has not yet been a study primarily focused on changes in steroids levels."
• Weight Gain: A consistent finding in the literature and confirmed by this study is that "smoking cessation leads to a weight gain." In this study, successful quitters gained an average of 6.8 kg over one year, with their mean BMI increasing from 26.2 kg/m² to 28.7 kg/m².
• SHBG Decrease (Significant): After one year of smoking cessation, a "statistically significant decrease in SHBG" was observed in former smokers. Crucially, "Changes in SHBG and testosterone did not correlate with BMI increase," suggesting a "direct effect of smoking cessation" on SHBG levels, likely due to changes in hepatic production.
• Testosterone Changes (Non-Significant): The study found "no significant changes in testosterone levels; decrease in total testosterone, free testosterone index and DHEAS was non-significant" after one year of abstinence. This contrasts with some previous reports of significantly lower testosterone in those who stop or reduce smoking.
• Cortisol and DHEA (No Change in Study): Unlike some literature that describes a "steep decrease in serum cortisol" after prolonged discontinuation of smoking and changes in the cortisol-to-DHEA ratio as a predictor of relapse, this study "did not show changes in blood levels of serum cortisol levels following the discontinuation of smoking" nor was the "cortisol and DHEA ratio" a predictor of success. The authors suggest observed higher cortisol levels might be due to stress from blood sampling.

3. Hormonal Predictors of Smoking Cessation Success:

• No Predictive Value: A primary aim of the study was to find a "possible predictor of successful smoking cessation among selected steroids." However, the study concluded that "monitored hormones could hardly predict success of smoking cessation." Basal samples of successful and unsuccessful quitters "did not differ" significantly in testosterone, DHEA, or cortisol.
• BMI as a Predictor (Inconsistent with Study): The literature suggests BMI can predict cessation success, with some studies showing "overweight men, unlike women, had a higher chance of successful smoking cessation." This study, however, did "not demonstrate that greater weight would predict success" as baseline BMIs were similar between successful and unsuccessful groups, though the study population was already overweight on average.

4. Mechanisms and Implications:

• SHBG and Testosterone: The study acknowledges the complex relationship between smoking, SHBG, and testosterone. The prevailing theory from other studies is that "higher total testosterone in smokers was due to SHBG increase." The observed "decrease in SHBG levels... without correlation to BMI" after cessation suggests a direct impact of smoking cessation on SHBG production, possibly hepatic.
• Testosterone Reduction Theories: Theories for smoking-induced testosterone reduction often point to a "direct effect of smoking on steroidogenesis" via enzymatic functions (e.g., inhibition of 3 alpha-hydroxysteroid dehydrogenase or changes in 7 alpha-hydroxylase and 6 beta-hydroxylase activity).
• Weight Gain Mechanism: Nicotine's ability to "increase energetic output and... reduce appetite" explains why smokers tend to have lower weight and why cessation leads to weight gain. However, the study noted heavy smokers might be heavier due to "other types of risk behavior, e.g. low physical activity and poor diet." Smoking also increases insulin resistance and central fat accumulation, raising the risk of metabolic syndrome and diabetes.
• Long-term Observation Needed: The study suggests that "It would be worth observing testosterone and SHBG levels after a longer period following the discontinuation of smoking, when the effects of chronic smoking could be eliminated."

Conclusion of the Study: The study generally aligns with the view that smoking's impact on the male reproductive system's hormonal homeostasis is "of little significance." While a significant decrease in SHBG was observed after one year of cessation (independent of BMI), other hormonal parameters (testosterone, DHEA, DHEAS, cortisol) showed no significant changes. Basal testosterone levels were not found to be useful in predicting smoking cessation success.