Is There a Link between Low Testosterone and Chronic Marijuana Use?

Will efforts to legalize medical marijuana lead to an increase in the incidence of low testosterone and related conditions such as gynecomastia?

Assuming greater availability leads to greater usage among at-risk groups, some doctors expect the answer to that question may be “yes.”

“Although the association between marijuana and gynecomastia hasn't been conclusively proven, it appears very plausible,” wrote Anthony Youn, MD, a plastic surgeon from the Detroit area, in a column for CNN Health.

“For this reason, the majority of plastic surgeons I've consulted with routinely inquire with their gynecomastia patients about cannabis use and recommend they stop smoking pot immediately.”

The uncertainty expressed by Youn and other doctors stems from conflicting research.

Some studies have found that frequent marijuana use leads to dramatic reductions in testosterone and, thus, to ancillary problems ranging from weight gain to infertility. Others have found no impact.

Research on the subject dates back at least four decades. Indeed, it was April 1974 when a team of authors that included the famed sex researcher William H. Masters published a much-cited piece in The New England Journal of Medicine.

That study found dramatic differences in hormone levels between a control group and 20 carefully selected marijuana smokers. Mean (± S.E.M.) plasma testosterone among 20 marijuana smokers, aged 18 to 28 was 416 ± 34 ng per 100 ml. For a control group of aged-matched men, the mean was 742 ± 29 ng per 100 ml. Moreover, the researchers noted, the quantity of marijuana smoked correlated strongly and negatively with testosterone levels.

Later that same year, the Journal published the account of another study by another team, this one led by Jack H. Mendelson, MD, that found no relationship between any level of marijuana use and testosterone levels.

Among 27 smokers in that three-week study no statistically significant changes in plasma testosterone levels were observed during and after the smoking period as compared with the pre-smoking base-line levels.

Moreover, the mean pre-use testosterone level of 12 casual users was 988 ±93 ng per 100 ml, while the mean pre-use level of 15 heavy users was higher — 1115 ±69 ng per 100 ml.

An additional 40 years of follow-up research has yielded more studies but very little additional clarity, at least among humans.

Among animals, however, trials show conclusively that THC, the active ingredient in marijuana, lowers testosterone, throws testosterone and estrogen out of balance and creates a host of problems.

“The risks far outweigh man boobs,” said Gregory Buford, MD, a plastic surgeon from Denver who worries about the effects of marijuana legalization despite the potential benefits to his breast-reduction business. “Estrogen dominance in a male has been clearly shown to increase the risk for cardiac events, stroke, and early death.”

The failure to reach definitive conclusions on marijuana’s medical effects, not just on testosterone but on a wide range of factors, stems largely from the difficulties of performing trials on an illegal substance.

As the drug creeps toward legalization, medical professionals expect better trials that will provide better guidance about the wisdom of further deregulation.

“My hope,” Buford said, “is that the medical profession will begin studying the potential link between frequent marijuana use, testosterone and estrogen levels and determine just how concerned we really should be.”