Cannabis and Testosterone

There are countless studies aimed at measuring the impact of marijuana use on men’s sexual health, particularly when it comes to testosterone production. A study conducted as part of a joint collaboration between the Reproductive Biology Research Foundation and the Missouri Clinical and Biochemical Laboratory found that cannabis does indeed have an impact on testosterone production. 

The Research Behind Marijuana and Testosterone:

  • The claim that marijuana causes man-boobs, aka gynecomastia, has more than likely originated from these few in-vitro studies (study, study), where crude marijuana extract had estrogenic effects on isolated rodent cells. Now, if something acts like estrogen, it can definitely induce some man-breast growth… However, it’s important to note that the studies were done on isolated cells taken from rats, and the whole experiment was conducted inside test-tubes. On top of that the effects haven’t been seen in in-vivo studies (inside a living organism).
  • It has been noted in several notable studies that THC (the active ingredient in cannabis) can potentially be an endrocrine disruptor in humans and animals, since it blocks GnRH secretion from the hypothalamus, which eventually leads to lowered LH and FSH production and therefore also lower testosterone production. THC has also been shown to inhibit several testicular enzymes needed in testosterone production in-vitro (study, study, study, study, study, study). Although it’s worth mentioning that in all of the studies I’ve seen, the effects have been reversible.
  • As weird as it is, some studies have shown that cannabis does not lower testosterone levels (study, study), despite the fact that a pile of studies has already shown that it does. Albeit, these review studies do contain research which shows cannabis to suppress testosterone, the abstracts still cleverly state that “chronic marijuana use showed no significant effect on hormone concentrations in either men or women.”.

For example, one of the studies from 1974 pointed to a lack of relationship between T levels and cannabis use in an investigating into pot smoking on T levels over a 21 day period. On average the volunteers of the study smoked 54 cigarettes each over the study period so they were more than just ‘occasional’ smokers. Similar results were reported in a 1991 study , where the authors wanted to investigate the effects of chronic weed use on reproductive and stress hormones. It was a big study, using 93 men and 56 women who were categorized based on how frequently they smoked-frequent, moderate, infrequent and non-users.  The result of the study found no significant effect on any hormone concentrations across groups. This included not only testosterone, but also follicle stimulating hormone, cortisol and luteinizing hormone.

Not all studies reported insignificant findings though- one study  found that in men aged between 18 and 28 years who smoked cannabis at least four days a week for a minimum of six months, T levels dropped from 742 to 416ng/dL. Whilst still in the ‘normal’ category of testosterone levels, it is very close to the cut off for ‘hypogonadism’ of 300ng/dL. This is more or less an exception when it comes to human studies though.

So nothing to worry about then?

Marijuana is a plant that is dried and used as a psychoactive – the active compound that provides the ‘high’ is referred to as THC.

In the mid 1970s a research paper proposed links between the use of marijuana, diminished testosterone and gynecomastia. This led to a spike in research projects up to the 1990s with people trying to see if the results were in fact significant.

Whilst there have been one or two studies reporting an association between weed and decreased T levels, the majority of research shows that there is little to no effect on not only testosterone levels, but other sex hormone sub sets either. Even if the testosterone lowering effects would be significant, it’s still reversible. One of the studies showed that 24 hours after smoking a joint, testosterone levels had returned back to pre-smoking levels.

One thing that does appear certain though is the effects of cannabis on sperm quality and fertility, with research suggesting that regular use of the drug can make sperm less fertile, lower sperm count and ultimately lead to infertility in men.