A Sword with Two Edges


You may know what testosterone can do for your strength, but did you also know that it is a contraceptive? That’s right, taking any synthetic testosterone will reliably make you infertile.
I’ve discussed the reason for this in other posts, but I’ll explain it again. Essentially, the brain drives the testicle to make sperm and testosterone with two hormones, FSH and LH. Think of the testicle as an engine that won’t run without the “gas” provided by these hormones. How much is gas delivered depends on how much testosterone is sensed by the brain. If enough is testosterone is present, the signal to make more decreased. So, with anabolic steroids, the brain figures that there is plenty of testosterone around (it doesn’t ask from whence it came) and it reduces the “gas” (LH and FSH) to the testicle. Thus, natural testosterone levels fall along with sperm production.
Recently, it became clear to me that milder, over the counter supplements such as DHEA or androstenedione can also have this effect. These are not the same as testosterone but are the building blocks for testosterone production. Importantly, they are available as over the counter supplements that do not require a doctor’s prescription to take.
Last week, I saw a patient who wanted a vasectomy reversal to have more children. He wrote down that he was taking creatine and other protein supplements, but when pushed further, he admitted to using DHEA. Worried about his sperm production, I checked LH and FSH levels and they were extremely low. No gas to the testis. No sperm being made. Based on this, I told him that his sperm count will be low or zero after a vasectomy reversal. Since then, he stopped the supplements and will wait several months before having the surgery. Luckily, in many cases, the effects of synthetic testosterone supplements are reversible when they are discontinued.
But, there are also ways to increase testosterone levels and maintain fertility. This is an important part of my practice as I treat young men with low testosterone who may want kids later on. It involves using pills or injections that stimulate “natural” or bioidentical testosterone production from the testicle. One way is to give the LH hormone (hCG) to stimulate the testicle to make testosterone. Given by a small needle injection several times weekly, it does the trick. Another method is to give pills called clomiphene citrate or tamoxifen that stimulate natural LH and FSH production. Since these medications are not approved by the FDA for men in the US, it is important to discuss benefits and side effects thoroughly before using them.
Is normal testosterone important for your health? Absolutely. But, like a sword, it is a hormone with two sharp edges. And such instruments should be wielded with skill and balance.