Marijuana attacks your precious testosterone in almost every negative way possible. One study after another has shown that cannabis lowers testosterone. For example one research team found that "a reanalysis of existing data established that testosterone levels are depressed both after smoking one marijuana cigarette and after intravenous infusion of delta-9-tetrahydrocannabinol, a pharmacologically active component of marijuana". The same study concluded that it would take at least 24 hours for testosterone levels to normalize after marijuana use. (NOTE: It's not just the smoke – an IV will do it.)
Another study found that not only was testosterone decreased after short term marijuana use, but leutenizing and follicle stimulating hormone were lowered as well. And just to add to the endocrinological misery, the arch-villain and stress hormone cortisol was raised as well. There are also studies in animals and humans that strongly indicate that marijuana blunts growth hormone response as well. And so it is no wonder that animal studies show that marijuana use shrinks the testes. So, if you're not happy with lowered testosterone, infertility and elevated cortisol, you can sit around enjoying the fact that you've got a little more air flow through your boxers.
You should also know that there are many reports that chronic marijuana use leads to gynecomastia, ie "enlarged male breasts", due to its abundant amounts of phytoestrogens. One journal writer pointed out that "given the effects of marijuana on the HPG axis in males and the possibility that noncannabinoid components of marijuana smoke have affinity to the estrogen receptor, an association with gynecomastia is plausible but has not been convincingly demonstrated". Remember that estrogen fights against testeosterone in the body as well.
Marijuana has also recently been flagged as particularly dangerous for young people because it decreases seratonin and increases norepineprine. While these are not sex hormones like testosterone, these can alter mood negatively and, through prolonged use, may permanently alter anxiety levels and reaction to stress. Again, the researchers are suggesting this may have long term, possibly lifetime anxiety and mood repercussions. I would also add that any increase in stress will also likely lower testosterone as well.
So we ask the question, "Could someone please explain again why anyone in their right mind would smoke marijuana?" The only thing we can think of is the extra hydrogen cyanide. That's right – marijuana tobaco is much higher in hydrogen cyanide – probably five times higher – than cigarette tobacco. Maybe that partially explains why habitual pot smoking is so hard on the lungs and why cannabis use has also now been linked to the most aggressive form of testicular cancer.
Not to make the bad news even worse, but there is also considerable reported evidence of erectile dysfunction among chronic marijuana users. This is undoubtedly partially due to the lowered testosterone. However, the other reason was discovered by one study that showed marijauna effected Nitric Oxide and summarized by saying, "We conclude that early endothelial damage may be induced by chronic cannabis use (and endocannabinoid system activation". Let me translate that: it may take your sex life with it. If so, decreased sexual activity is also associated with lowered testosterone levels as well.
The tragedy with marijuana is that many cultures and youth are embracing marijuana as more "natural", but this is far from being the case. One recent study found that marijuana induces just as much cell toxicity and DNA damage as cigarette smoke. The researchers were very clear that marijuana displayed just as much cancer causing power as the cigarette smoke: "In addition, when corrected for total particulate matter yield, little difference was observed in the mutagenic activity of samples smoked under the extreme vs the standard regime for both tobacco and marijuana condensates ".
In summary, there is significant evidence that marijuana lowers testosterone, nitric oxide, leutinizing hormone, growth hormone and raises cortisol at the same time. Hormonally, there is no justifiable reason for cannabis use.