SHBG and testosterone: what TikTok gets right and wrong

What did @mrjabarov actually say?

The video gives a basic rundown of sex hormone-binding globulin, covering what it binds to, why that matters, and what happens when levels drift too high or too low. The creator says SHBG "binds to testosterone and estrogen and makes them inactive" and that only "unbound hormones are available to the receptors." He frames SHBG as a natural regulator that prevents hourly hormone swings and argues the goal should be an "optimal range," not suppression. For men, he puts that range at 20 to 13 nmol/L. For women, he says "around 60."

The framing is reasonable for a 60-second explainer aimed at people new to hormone labs. The core biology is not invented. But there is a meaningful factual error buried in the numbers, and one mechanistic simplification that deserves more scrutiny than the format gives it.

Does the science back this up?

Mostly, yes, with real caveats. SHBG is a glycoprotein produced primarily in the liver. It binds testosterone and estradiol with high affinity, rendering them biologically inactive for most tissues. Free hormone plus albumin-bound hormone make up what labs call "bioavailable" testosterone. This is not contested.

The claim that SHBG prevents hourly fluctuations is supported in the literature. Pardridge (1988, Endocrine Reviews) described SHBG as a plasma buffer that dampens the amplitude of pulsatile hormone release. Anderson (1974, Clinical Endocrinology) established the basic binding kinetics still referenced in clinical practice today.

The "estrogen dominance" framing when SHBG is low is where things get shakier. Low SHBG does correlate with higher free estradiol in some contexts, particularly in women with metabolic syndrome, as shown by Ding et al. (2007, JAMA). But "estrogen dominance" as a clinical diagnosis remains poorly defined and is not a standard term in endocrinology. The creator uses it loosely, which is a pattern worth noting.

What did they get wrong (or right)?

The reference range stated for men is flat-out wrong as presented. The creator says the optimal range for men is "20 to 13" nmol/L. That is listed in reverse order, and more importantly, 13 nmol/L is below most established lower reference limits. The Mayo Clinic and LabCorp both cite adult male reference ranges of approximately 16.5 to 55.9 nmol/L, depending on age. Calling 13 nmol/L part of an optimal range, without qualification, is inaccurate and could mislead someone reviewing their lab work.

The women's figure of "around 60" nmol/L is plausible as a midpoint but is presented without any acknowledgment that female SHBG ranges shift dramatically with age, menstrual cycle phase, oral contraceptive use, and pregnancy. Plymate et al. (1988, Journal of Clinical Endocrinology and Metabolism) documented these shifts clearly.

What the creator got right: SHBG is not the enemy. The instinct to frame it as a regulator rather than something to suppress at all costs is clinically sound and pushes back against bad advice that circulates freely in TRT communities.

What should you actually know?

If you are reviewing your own hormone panel, a few things matter more than a single number. First, free testosterone is calculated or measured in context with total testosterone and SHBG together. A high SHBG with high total testosterone may still produce adequate free testosterone. Second, SHBG is heavily influenced by modifiable factors: alcohol intake, thyroid function, insulin resistance, and liver health all move it. Goto et al. (2007, Diabetes Care) showed that insulin resistance is one of the strongest suppressors of SHBG in men.

Third, the reference range question is genuinely complicated. Optimal is not the same as normal, and what is optimal depends on symptoms, age, and clinical context. No TikTok video, including well-intentioned ones, can substitute for a clinician interpreting your specific labs. If your SHBG sits outside whatever range a social media creator cites, that alone is not a diagnosis or a reason to take action.