High natural testosterone at 43: what the numbers actually mean

What did @onehottrail actually say?

The video features a 43-year-old man with a total testosterone of 1,200 ng/dL and free testosterone of 126 pg/mL. The creator, tagging Nurse Doza, identifies this as a problem: good total production but poor free testosterone availability, pointing to elevated SHBG around 100 nmol/L. The proposed explanation is that his weekly 36-hour fast is "the biggest contributing factor" to the elevated SHBG, with diet, supplements, and sauna mentioned as secondary context.

The framing is reasonable for a short-form video. The numbers given are internally consistent, and the creator correctly identifies that roughly 1% free-to-total ratio signals high SHBG rather than a production problem. That's an accurate read of the lab math.

Does the science back this up?

Mostly, yes. Caloric restriction and prolonged fasting do raise SHBG, and the mechanism is reasonably well established. But the magnitude claimed here, around 100 nmol/L, sits at the high end of what fasting alone typically produces.

A 2022 review by Grossmann and Matsumoto in the Journal of Clinical Endocrinology and Metabolism confirmed that energy deficit reliably increases SHBG, likely through reduced insulin signaling in the liver, since insulin suppresses SHBG synthesis. Fasting drops insulin, so SHBG rises. That chain of logic is sound. However, SHBG at 100 nmol/L is roughly 2-3 times the upper end of most reference ranges (typically 10-57 nmol/L for adult men), and studies on intermittent fasting protocols show more modest SHBG increases, generally 10-20% above baseline (Antoni et al., 2017, Obesity Reviews). A weekly 36-hour fast producing SHBG that high would be an outlier, not a standard finding. The creator is right to say "there does seem to be something else going on."

What did they get wrong (or right)?

Credit where it's due: the creator correctly flags that high total testosterone with low free testosterone points to a binding problem, not a production failure. That distinction matters clinically and gets missed in a lot of online testosterone content.

The sauna caveat is also honest. Saying "we don't have that much evidence on testosterone itself" is accurate. Most sauna research focuses on sperm parameters and heat stress, not on SHBG specifically. Claiming restraint there is more credible than overclaiming.

Where the video falls short is in the SHBG math. Estimating SHBG at "around 100 nmol/L" from a free testosterone of 126 pg/mL and total of 1,200 ng/dL is plausible, but SHBG calculation is sensitive to albumin assumptions and the formula used. Presenting an estimate as a near-certain figure without caveating it as a calculation rather than a measured value is a small but real gap.

More importantly, the creator recommends getting "some checked" at the end without specifying what. SHBG should be directly measured, not estimated, and conditions like hyperthyroidism, liver disease, and certain genetic variants can drive SHBG this high regardless of fasting. That list needed to be said plainly.

What should you actually know?

If your total testosterone looks fine but you feel symptomatic, free testosterone and SHBG are the next numbers to pull. Calculated free testosterone has limitations; direct SHBG measurement is the more reliable starting point.

SHBG above 70-80 nmol/L in a man without an obvious dietary explanation warrants a differential workup. Hyperthyroidism is the big one to rule out: thyroid hormones directly stimulate hepatic SHBG production, and the effect can be dramatic. Liver disease, anticonvulsant use, and some androgen receptor pathway variants also push SHBG up significantly (Selva and Hammond, 2009, Trends in Endocrinology and Metabolism).

As for fasting specifically: the evidence supports a real but moderate effect on SHBG. If someone is already lean and doing weekly prolonged fasts, stacking caloric stress on top of a low-insulin baseline could amplify the effect. But treating fasting as the sole explanation for SHBG at 100 nmol/L without ruling out thyroid and liver function first is getting ahead of the data.

Bottom line: is this video worth 51K views?

Mostly. The core hormone physiology here is accurate, and the creator shows appropriate uncertainty about sauna data. The recommendation to get labs checked is the right call, even if it's vague. The weakest part is framing a 36-hour weekly fast as a likely sufficient cause for SHBG this elevated without a stronger push toward ruling out thyroid or hepatic pathology. For a TikTok this is above average. For someone using it to make decisions about their own labs, it should be a starting point, not a conclusion.