He stood there looking at me, as deflated as an old circus balloon. “Doc, I heard that testosterone is important for my fertility, so that’s why I started taking it. I had no idea my sperm count would drop!”
Sure, testosterone is good for you. It’s critical for good overall health and for normal fertility. But more isn’t necessarily better. You see your body has its own way of regulating hormones and does it quite precisely I might add. Probably better than most home thermostats. But if you perturb the system by taking hormones, it throws it out of balance.
Testicle as Orchid
Allow me an analogy here. Imagine that the testicle is a plant, say an orchid. Not a bad choice as the Greek word for testicle is actually orkhis. Anyway, think of the blooming orchid as a testicle that is making sperm. When conditions are right, the orchid blooms and the testicle makes mature sperm. When they are not right, the plant subsists but does not bloom and the testicle simply makes fewer or no sperm.
Now, let’s go a little further. To get an orchid to bloom, it needs the proper amount of water and sunlight (indirect of course). To get a testicle to make sperm, it needs the proper amount of testosterone (water) and follicle stimulating hormone (FSH, sunlight). You may be able to eke out a few sperm with only water or only sunlight, but not normal amounts and counts.
The Pituitary Gardener
Now the gardener tending this orchid is the pituitary gland. It controls how much water (testosterone) and sunlight (FSH) that the orchid (testicle) sees. The one fault of this gardener though is that he can only give the orchid water and sunlight together, and not separately, and he makes the decision to give both on how much water (testosterone) he senses is around.
You with me? Good, let’s keep going. One day the gardener notices that it has rained a lot recently; that is, that the man who owns the testicle has taking testosterone supplements. He looks at the plant and says: “Plenty of water here, no need for more water (or sunlight).” So, yes it’s true that the orchid has plenty of water (testosterone), but it still needs sunlight (FSH) to bloom, which is precisely what the gardener withholds. In this state, the orchid will subsist but will not bloom, just as the testicle will subsist but not make sperm. Until the balance of hormones returns after stopping the testosterone supplements, sperm counts will be low or even zero. And it may take 3-6 months to get the testicle to make sperm again, once the proper hormone balance returns.