I had read about a Prozac-to-testosterone connection, but what he wrote really prompted me to study it in more depth:
“I ask because I’ve been doing some thinking on when things got bad for me back in February before I was diagnosed with low testosterone. It all started with insomnia that finally “snapped” into a chronic fatigue state, including moderate-high brain fog, memory, and concentration issues…Then after a week of this I went to my previous doc and got prescribed fluoxetine (Prozac), after which things went to s__t: insomnia got a lot worse, as did anxiety, I started having a leg twitch, ED, intense brain fog and concentration (I could barely read), feeling hot/flushed for short periods of time, and a few other things.”
Basically, he had a lot of apparent side effects from the Prozac and he asked if it could lower testosterone. Of course, I had no doubt that Prozac sometimes lowers testosterone, because anything that decreases the frequency of sexual intercourse and lowers dopamine will likely lower your T a little. (For more information, see my page on Testosterone and Dopamine.) And, sure enough, I found that in the last five years a group of papers have come out showing that Prozac often negatively alters our “man juice” as I have heard it called.
Consider the following studies:
“Sperm motility and density were also significantly reduced in cauda epididymides and testes of the treated group. The weights of reproductive organs (testes, epididymides, ventral prostrate and seminal vesicle) were decreased considerably. The hormonal assay also showed significant decrease in testosterone levels and FSH levels. Testicular cell population dynamics also demonstrated a decrease in the number of both primary and secondary spermatocystes and spermatids in the treatment group.”
Does it get much worse than that? Shrunken testes? Sperm reductions? This was definitely not good news.
2. Early Studies Deny Change in Testosterone. A couple of studies even came out that said, in spite of the fact that Prozac can negatively alter libido and sexual function, there was no significant change in testosterone. One of these was on animals  and one on humans.  However, the latter study admitted that a) their study was small, b) some patients did experience a loss in testosterone and c) that there were published case studies of testosterone reductions.
Therefore, the conclusion is that Prozac will likely negatively alter almost of your “male sexual parameters,” including testosterone, libido and fertility, especially if given enough time. Now does this mean that you should not use an SSRI, especially considering the fact that they have been shown to be little better than placebo for mild to moderate depression? Of course, that is something that you must discuss with your doctor. Some men, especially those with more serious and severe depression, gain significant improvement from Prozac and other SSRI’s. So “any port in a storm” as they say.
NOTE: See also my page on How Prozac Often Increases Prolactin, which can lower testosterone in and of itself potentially. More importantly, this will often impact libido.
However, I would discuss other options with your doctor. Perhaps Wellbutrin (which can have nasty side effects) or some other medication will work just as well without the side effects. You may also be able to gain substantial relief by going a more natural route. See my page on Natural Depression Cures for more information.
CAUTION: Few men realize just how serious depression is. Depression can lead to actual brain and neuron damage: it sets off a wave of inflammation, oxidation and (often) elevated cortisol that can literally shrivel key lobes between your ears including the hippocampus. It’s also associated with heart disease and lowered testosterone. (See my page on Depression In Men for more details.) So do NOT just quit an SSRI without discussing it with your doctor first. Furthermore, some experts believe that they are very dangerous during transitional phases, i.e. when you are starting up or stopping an SSRI or when you are switching from one SSRI to another. Their research and clinical experience shows that this can lead to suicide and other extreme psychological behavior.
2) Neuro Endocrinology Letters, 2007, 28(3):321-325, “Effects of long-term use of fluoxetine on fertility parameters in adult male rats”
3) Physiology & Behavior, Mar 1996, 59(3):479 485, “Male reproductive systems under chronic fluoxetine or trimipramine treatment”
4) Annals of Clin Psychiatry, 2006, 18(1):19-22, “Fluoxetine Treatment and Testosterone Levels”
5) Amer J of Psychiatry, 2010, “Treatment of Resistant Depression in Adolescents (TORDIA): Week 24 Outcomes”
6) Archives of General Psychiatry, 2010, “Recovery and Recurrence Following Treatment for Adolescent Major Depression”
7) J. Pharm. Biomed. Sci., 2012, 2(7):87-93, “The Effects of Fluoxetine Usage on the Concentration of Testosterone Hormone”