@daviddemesquita's TRT fertility claims need context

What did @daviddemesquita actually say?

The claim is that exogenous testosterone lowers SHBG, and low SHBG correlates with conceiving girls, while higher SHBG correlates with boys. His recommendation: stop testosterone about 30 to 37 days before trying to conceive, giving SHBG time to rise and sperm time to "load up" with male-chromosome genes.

To his credit, he hedges. He calls it "not a perfect science by any means" and frames his 30-day window as a personal wager, not a clinical protocol. That caveat matters a lot here, because the underlying science is considerably weaker than the framing suggests. He is presenting a correlation as an actionable fertility strategy, and those are very different things.

He also states the half-life of sperm is 40 days, which he uses to justify timing intercourse. The biology here is real but the logic built on top of it is shaky.

Does the science back this up?

Partially, but not in the way this video implies. The SHBG-sex-ratio link exists in the literature, but it is weak, contested, and almost certainly not something you can engineer by cycling off testosterone for a month.

The foundational study people cite is Mathews et al. (2008, PLOS ONE), which found that women with higher serum testosterone at conception were slightly more likely to have boys. A separate line of research, including work by Fukuda et al. (1996, Human Reproduction), suggested that stressful conditions, which tend to alter androgen and SHBG levels, correlated with fewer male births. Neither study was designed to test the intervention @daviddemesquita describes.

The SHBG-to-sex-ratio mechanism he is referencing is largely speculative. No randomized controlled trial has tested whether manipulating male SHBG levels by stopping TRT changes offspring sex ratio. The sperm biology here is also more complex than presented. X- and Y-bearing sperm do not differ in survivability in any clinically meaningful way under normal conditions, according to Aitken et al. (2014, Human Reproduction Update).

What did they get wrong or right?

The testosterone half-life figures are roughly accurate. Testosterone cypionate and enanthate typically clear in 14 to 21 days, and serum levels drop noticeably within 7 to 10 days of the last injection. That part checks out.

The 40-day sperm half-life figure is in the right ballpark. Spermatogenesis takes approximately 64 to 74 days in total, with sperm maturation in the epididymis adding another 12 to 21 days. Exogenous testosterone suppresses the hypothalamic-pituitary-gonadal axis and reduces sperm production, sometimes to azoospermia. Recovery after stopping TRT typically takes 3 to 6 months, not 30 to 37 days, based on Liu et al. (2006, Journal of Clinical Endocrinology and Metabolism).

That is the bigger problem. His 30-day window is probably too short to meaningfully restore spermatogenesis, let alone optimize it. Recommending men try to conceive 30 days after stopping TRT, when sperm counts may still be severely suppressed, could actually reduce fertility rather than improve it.

The SHBG-sex-selection mechanism is the weakest link. SHBG is primarily a female-side variable in the studies cited. Applying it to male SHBG as a sex-selection lever is a creative extrapolation, not an established pathway.

What should you actually know?

If you are on TRT and want to conceive, the fertility conversation starts much earlier than 30 days before trying. Exogenous testosterone suppresses sperm production in the majority of men, and recovery is not guaranteed within a month. A reproductive endocrinologist or urologist specializing in male fertility should be involved before you stop TRT, not after.

Medications like clomiphene citrate or human chorionic gonadotropin (hCG) are used clinically to preserve or restore fertility in men on testosterone therapy, and those conversations require a licensed provider and a semen analysis, not a TikTok timeline.

On the sex-selection question: the honest answer is that no evidence-based, non-invasive method reliably determines offspring sex. Preimplantation genetic testing during IVF is the only clinically validated approach. Everything else, including SHBG cycling, dietary changes, and timing intercourse, operates in the realm of anecdote and weak observational data.

• If fertility is your goal, get a baseline semen analysis before stopping TRT.
• Sperm recovery after TRT cessation averages 3 to 6 months, not 30 days.
• The SHBG-sex-ratio link has not been tested as a male-side intervention in any clinical trial.
• Talk to a reproductive urologist before making any changes to your TRT protocol.