The effects of cannabis on the hormonal system and male fertility remain controversial within the scientific community.
A study conducted by the University of Geneva (UNIGE), in collaboration with the Swiss Centre for Applied Human Toxicology (SCAHT), provides new insights. It shows that cannabis consumption does not decrease testosterone levels in young men, and may even increase its testicular synthesis.
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This hormonal increase cannot, however, be directly linked to fertility. These findings are based on blood analyses conducted on 94 Swiss conscripts. The team also identified two new hormonal biomarkers that could be used to track regular cannabis use. The study is published in the journal
Communications Medicine.
Some studies suggest that cannabis could reduce sperm count, concentration, and motility. These effects would be related to the endocannabinoid system, a network of chemical messengers and receptors present in the brain and reproductive organs, which interacts with sex hormones.
However, the conclusions of research conducted so far—particularly the impact of cannabis consumption on testosterone—have often been contradictory.
To learn more, a team led by Serge Rudaz, professor at the Section of Pharmaceutical Sciences of the Faculty of Sciences at UNIGE, in collaboration with SCAHT, performed an in-depth analysis of steroid hormones—including sex hormones such as androgens, progestogens, and estrogens—in blood plasma samples from Swiss conscripts aged 18 to 23.
The cohort included 47 confirmed cannabis users and 47 non-users. The major novelty of this study lies in extending the analysis to hundreds of hormones, whereas previous work focused only on testosterone.
The results show that cannabis consumption would lead to an increase in testosterone of about 23% in young men.
Increase in testosterone
"Our results show that cannabis consumption would lead to an increase in testosterone of about 23% in young men," reveals Serge Rudaz. "But by looking more closely at all male sex hormones—androgens—we were able to pinpoint the source of this increase specifically in the testicles. Androgens produced by the adrenal glands, on the other hand, were not affected by this increase." Cannabis would thus have a direct action on the testicles, and more specifically on Leydig cells, which produce testosterone.
Thanks to this extended analysis, the team also managed to identify two new potential biomarkers of cannabis use: hydroxyprogesterone (11B-OHP4) and dihydroprogesterone (5B-DHP4).
"These are two metabolites derived from progesterone, another important sex hormone. The increase in their concentration in users is so high that they could be used to track endocrine disruptions linked to regular cannabis exposure. Above all, this discovery should encourage the research community to broaden studies to new, previously overlooked hormones that could also play a role in the male reproductive system," says Mathieu Galmiche, former postdoctoral researcher at the Section of Pharmaceutical Sciences of UNIGE, now affiliated with the Karolinska Institutet in Stockholm, and first author of the study.
No link with sperm quality
The increase in hormone levels among cannabis users should not, however, be interpreted as an indicator of sperm quality. The link between testosterone and fertility remains very complex to decipher. Moreover, the observed increase could be a compensatory response of the body to reduced sensitivity of certain androgen receptors in the presence of cannabis.
It is also possible that men with naturally high testosterone levels are more prone to taking risks and therefore to using cannabis.
While cannabis appears to disrupt certain biological processes related to reproduction, the exact clinical consequences on young men's fertility will still need further research to determine the mechanisms, toxicity thresholds, and long-term effects.