Although cannabis appears to disrupt certain biological mechanisms related to reproduction, the exact clinical consequences on the fertility of young men are still being studied.
Photo Credit: Esteban López
Scientific Frontline: Extended "At a Glance" Summary: Cannabis Use and Male Testosterone Levels
The Core Concept: A recent study demonstrates that cannabis use in young men does not reduce testosterone levels, but instead appears to increase the testicular synthesis of the hormone by approximately 23%.
Key Distinction/Mechanism: Contrary to earlier assumptions that cannabis decreases male sex hormones, this research localized the testosterone increase specifically to the testes (Leydig cells), rather than the adrenal glands. Importantly, the study clarifies that this hormonal spike does not equate to improved sperm quality or overall fertility and may represent a compensatory physiological response.
Major Frameworks/Components:
- Extensive steroid profiling that analyzed hundreds of hormones (including androgens, progestogens, and estrogens), expanding significantly beyond isolated testosterone screening.
- Examination of the endocannabinoid system's interaction with male reproductive biology.
- The isolation of two novel metabolic biomarkers indicating regular cannabis exposure: hydroxyprogesterone (11B-OHP4) and dihydroprogesterone (5B-DHP4).
Branch of Science: Endocrinology, Toxicology, and Pharmaceutical Sciences.
Future Application: The discovery of two new progesterone-derived metabolites provides clinicians and toxicologists with novel biomarkers to accurately track regular cannabis exposure and monitor related endocrine disruptions in patients.
Why It Matters: This study resolves conflicting scientific narratives regarding cannabis and male hormones by proving that usage actually elevates testosterone levels. It fundamentally shifts the research paradigm, encouraging the scientific community to evaluate previously overlooked hormones when assessing male reproductive health.
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 Center for Applied Human Toxicology (SCAHT), provides a new answer by showing that cannabis use does not reduce testosterone levels in young men and may even increase its testicular synthesis. However, this increase in hormone levels cannot be directly linked to fertility. These conclusions are based on a detailed analysis of plasma samples from 94 Swiss conscripts. In addition, the researchers identified two new hormonal biomarkers that may help detect regular cannabis use. The findings have been published in Communications Medicine.
Some studies suggest that cannabis may reduce sperm count, concentration, and motility. These effects are believed to be linked to the endocannabinoid system—a network of chemical messengers and receptors in the brain and reproductive organs that interacts with sex hormones. However, the findings of studies conducted so far—particularly regarding the impact of cannabis use on testosterone—have often been contradictory.
To investigate further, a team from the Section of Pharmaceutical Sciences at the UNIGE Faculty of Science, led by Professor Serge Rudaz and in collaboration with SCAHT, conducted 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 nonusers. The major innovation of this study lies in extending the analysis to hundreds of hormones, whereas previous research focused solely on testosterone.
Increase in Testosterone
“Our results show that cannabis use would lead to an increase of about 23% in testosterone in young men,” explains Serge Rudaz. “But by taking a closer look at all male sex hormones—the androgens—we were able to locate the source of this increase specifically in the testes. Androgens produced by the adrenal glands were not affected by this increase.” Cannabis therefore appears to have a direct effect on the testes, and more specifically on Leydig cells, which produce testosterone.
Thanks to this broader analysis, the team was also able to identify two potential new biomarkers of cannabis use: hydroxyprogesterone (11β-OHP4) and dihydroprogesterone (5β-DHP4). “These are two metabolites derived from progesterone, another important sex hormone. The increase in their concentration among users is so high that they could be used to monitor endocrine disruptions linked to regular cannabis exposure. Above all, this discovery should encourage the scientific community to expand studies to new hormones that have so far been overlooked, and which may also play a role in the male reproductive system,” explains Mathieu Galmiche, a former postdoctoral researcher in the UNIGE Section of Pharmaceutical Sciences, now at the Karolinska Institutet in Stockholm and the study’s first author.
No Link to Sperm Quality
However, this increase in hormone levels among cannabis users should not be interpreted as an indicator of sperm quality. The link between testosterone and fertility remains very complex to decipher. Furthermore, the observed increase could represent a compensatory response by the body to reduced sensitivity of certain androgen receptors in the presence of cannabis. It is also possible that men with naturally higher testosterone levels are more prone to risk-taking behavior and, consequently, more likely to use cannabis.
While cannabis appears to affect certain biological mechanisms related to reproduction, the exact clinical implications for the fertility of young men remain unclear. Further research is needed to determine whether a toxicity threshold exists and to assess potential long-term effects.
Published in journal: Communications Medicine
Title: Cannabis consumption is associated with altered steroid metabolism in young men
Authors: Mathieu Galmiche, Isabel Meister, Fanny Zufferey, Michel F. Rossier, Rita Rahban, Alfred Senn, Serge Nef, Julien Boccard, and Serge Rudaz
Source/Credit: Université de Genève
Edited by: Scientific Frontline
Reference Number: bio052826_01
