Idiopathic Male Infertility: What MOXI Actually Found About Antioxidants
A single patient, three years into an unexplained infertility workup, already seven months into an over-the-counter supplement he started on his own. The disagreement isn't just whether to stop it — it's whether anything empiric, supplement or injectable, belongs in its place.
Marcus T., a 38-year-old commercial airline mechanic, has been trying to conceive with his wife for three years — long enough that they’ve been through the standard workup twice, and long enough that Marcus started an over-the-counter “male fertility” antioxidant supplement on his own seven months ago after reading about it online. His hormones are unremarkable and his anatomy is normal; what’s left is a diagnosis of idiopathic oligoasthenospermia, a low count and low motility with no identifiable cause, and a semen analysis that has not improved since he started the one intervention he chose for himself.
It may have moved the other way. His concentration seven months ago, before the supplement, was 12 million/mL with 32 percent motility; today it is 9 million/mL and 28 percent — a real decline, not a rounding difference, over the exact interval he’s been taking it. That trend lines up uncomfortably well with what the largest trial of this supplement class actually found: the MOXI trial, a 174-man, nine-center randomized study, showed sperm concentration falling by a median of 4.0 million/mL on the antioxidant formulation over three months against a 2.4 million/mL rise on placebo — a statistically real difference in the wrong direction — and live birth at six months numerically lower on the antioxidant arm, 15 percent against 24 percent, though the trial wasn’t built with enough power to call that endpoint on its own. Recombinant FSH is the other empiric option on the table, with real support from European trials in men with normal gonadotropins and no other explanation — but it carries no US indication for this use, and after three years, the honest next conversation may be less about which empiric drug to try third and more about whether it’s time to stop trying empiric drugs at all.
In the reproductive endocrinology clinic, after three years
Stop the supplement. MOXI is the largest, best-controlled trial we have on this exact product category, and it didn't just fail to show benefit — concentration moved in the wrong direction relative to placebo. His own numbers over the same seven months look like a small-scale replication of that finding, not a coincidence I'd keep betting against.
I'd be careful reading too much into one man's trend against a trial average, and MOXI wasn't powered for live birth — the endpoint that actually matters to him. The supplement is low-risk and he believes it's helping him do something proactive after three hard years. I wouldn't take it away without offering something in its place.
Calling the trial 'underpowered for live birth' is true, but it doesn't rescue the concentration finding, which was adequately powered and went the wrong direction — that's not a null result we're overriding, it's a signal.
I don't think the answer is to swap one empiric agent for a costlier one. FSH's European evidence comes from smaller, more heterogeneous trials than MOXI, and it has no US indication for idiopathic infertility — starting it here repeats the same pattern he's already lived through with the supplement, just with an injection instead of a capsule.
After three years and a stable idiopathic diagnosis, referral for assisted reproduction is a more honest next step than a third unproven empiric trial. That doesn't mean FSH is never reasonable — it means it belongs in a conversation with a reproductive specialist who can weigh it against IUI or IVF directly, not as something we add today because the last thing didn't work.
Agreed: stop the antioxidant supplement today, and refer for a reproductive endocrinology consultation to discuss intrauterine insemination or in vitro fertilization directly, given three years of unexplained infertility.
Not agreed: whether empiric FSH has any legitimate place in his care at all, or whether it’s simply the supplement’s problem wearing a prescription. The urologist would raise it as a bridge option pending the ART consultation; the pharmacologist would let the reproductive specialist decide with the full comparison in hand, rather than start it today and hand it off half-tried.