However, the specific mechanisms remain unclear, future research should further explore the reasons for age differences to validate and refine our findings. This mechanism may attenuate the effect of cotinine on testosterone. However, it is hypothesized that the activation of autophagy or apoptosis in Leydig cells will directly inhibit testosterone biosynthesis35–37. This association remained statistically significant following adjustments for potential confounding variables. After stratified analysis by age, we also found an inflection point of 508 in people aged 50 and above, as shown in Table 3. Univariate and multivariate analyses by the weighted linear model. Continuous variables are weighted mean ± SE, the p-value was calculated by a weighted linear regression model. There were statistically significant differences between quartiles of serum cotinine in all outcomes. Table 1 shows weighted baseline characteristics of study participants. In addition, the age-based subgroup was also analyzed using the same statistical procedures described previously. When considering the connection between nicotine and testosterone, it’s crucial to understand how this widely used substance can influence hormone balance. Hormonal imbalances—like low testosterone levels—can lead to symptoms such as fatigue, decreased libido, and changes in mood. Balance My Hormones helps men and women restore their hormones to optimal levels through bespoke TRT and HRT treatment plans. Mike has over 25 years of experience in the healthcare sector, much of that working with people who have hormone imbalances. Some studies report slightly higher T levels in smokers but these results are inconsistent, likely influenced by other factors. Studies show conflicting results regarding nicotine’s impact on testosterone. Men dealing with low testosterone should look for reliable treatments like TRT rather than turning to smoking, which only worsens overall health. So, it is best to avoid smoking altogether and look for proven ways to increase reproductive hormones like TRT. And smoking’s potential hormonal effects don’t outweigh its negative health effects like lung cancer, respiratory diseases, heart disease and asthma. Any short-term testosterone increase (if there is any) comes with significant risks to reproductive and overall health. The researchers noticed that as the duration of smoking increased, serum testosterone declined more significantly. The study also suggested that smoking raising testosterone may partially underlie the association of smoking with cardiovascular disease. A systematic review and meta-analysis of observational studies published in Science Direct found that smokers had lower testosterone after stopping or reducing smoking. The study found that smokers had lower levels of bioavailable testosterone than non-smokers. This age difference suggests that the relationship between serum cotinine and testosterone may be influenced by age-related factors. In contrast, our study employed a larger sample size, utilized serum cotinine levels as the independent variable, examined a more comprehensive range of tobacco products, and implemented rigorous control measures for confounding variables. Consequently, there is a potential for competitive inhibition of androgen glucuronidation by nicotine and its metabolites, leading to an increase in androgen levels14,16,30–32. However, the specific mechanism through which elevated cotinine may lead to an increase in total testosterone remains uncertain, prompting consideration of various potential explanations.