Primate study suggests chronic cannabis use may impact male reproductive health

1st February 2022

Chronic cannabis use may have an impact on the male reproductive system and could result in primary testicular failure, a new report found.

Clinician-scientists at the Oregon National Primate Research Centre at Oregon Health & Science University concluded that chronic exposure to THC, the psychoactive compound in cannabis, could lead to “significant dose-response testicular atrophy”, among other effects.

The researchers monitored healthy male nonhuman primates – rhesus macaques, to be more precise – after administering THC edibles over a seven-month period. At follow-up, it was discovered that THC exposure had had an impact on the animals’ reproductive health.

It is reported that, while there were no significant changes in semen parameters, in total, average bilateral testicular volume decreased by 58%.

The study’s senior author Jamie Lo, M.D., M.C.R. said: “Our analysis of the collected samples found that THC use was associated with significant adverse impacts to the animals’ reproductive hormones, including decreased levels of testosterone and severe testicular shrinkage.

“Specifically, we observed a greater than 50% decrease in testicular size.

“Unfortunately, these effects appeared to worsen as the THC dose was increased, suggesting a possible dose-dependent effect.”

The exposure to THC was increased every 70 days until the dosage reached the equivalent of a heavy medical cannabis dose in humans.

The data collected showed that an increased THC dosage had a significant impact on a number of levels.

Researchers found that significant dose-response decreases in mean total testosterone level, oestradiol level, but increases the levels of follicle-stimulating hormone, luteinizing hormone and prolactin.

This study demonstrates that chronic cannabis use – and it should be emphasised that we’re talking about chronic cannabis use – could very well result in significant issues in male reproductive health. Furthermore, such heavy exposure may also have an impact on testicular function.

Study lead author Jason C. Hedges, M.D., PhD, associate professor of urology in the OHSU School of Medicine, said: “While more research is necessary to better understand the potential long-term impacts of THC in humans, these early findings are concerning from a clinical standpoint.

“As the prevalence of edible marijuana use continues to increase in the U.S. and worldwide — particularly in males of prime reproductive age — even moderate doses could have a profound impact on fertility outcomes.

“While family planning may not be top of mind for those in their late teens and early 20s, the longer-term effects of THC on male reproductive health are not well-defined; it is possible that THC could cause lasting impacts that may alter family planning later in life.”

Another recent study concluded that cannabis exposure was associated with a decrease in sperm counts and motility in mice. While both studies only tested the effects of cannabis in animals, the close similarities between macaques and humans may present some of the most concrete evidence so far of the potential side effects of chronic cannabis use in human males.

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