SHBG and testosterone: what the TRT community gets wrong

What did @socalurologyinstitute actually say?

The urologist behind this account gave a pretty clean explainer on sex hormone binding globulin. SHBG, they said, is a protein that binds testosterone and renders it "inactive." They argued it matters most during diagnosis, when a man's total testosterone looks fine on paper but his free testosterone is actually low. Once someone is on TRT, though, they dismissed SHBG monitoring and said online advice about lowering it is not effective: "I don't believe that's true." Their bottom line was simple: use it to make the diagnosis, then ignore it.

The framing is aimed squarely at men who've been told their testosterone is normal but still feel symptomatic. That's a real and underserved conversation. But some of the nuance got lost.

Does the science back this up?

Mostly, yes. The role of SHBG in obscuring true androgen status is well-documented, and the criticism of over-relying on total testosterone alone is legitimate. Where things get murky is the claim that SHBG becomes irrelevant once TRT starts.

SHBG does bind testosterone and estradiol with high affinity, leaving only free and albumin-bound fractions bioavailable. The Vermeulen formula, widely used in clinical practice, uses SHBG to estimate free testosterone precisely because total T is often misleading (Vermeulen et al., 1999, Journal of Clinical Endocrinology and Metabolism). That part the creator got right.

On the "don't worry about it after TRT" point, the evidence is more complicated. A 2020 study in JCEM found that SHBG levels influence free testosterone response to TRT and that men with high SHBG may need higher doses to achieve equivalent free T levels (Finkelstein et al., 2020, JCEM). That's not a trivial detail to dismiss. SHBG also fluctuates with liver function, thyroid status, obesity, and medications, all of which can shift during TRT management.

What did they get wrong (or right)?

They got the diagnostic framing right. Using SHBG alongside free testosterone to evaluate symptomatic men with borderline total T is standard-of-care thinking, consistent with the American Urological Association's 2018 testosterone deficiency guidelines.

Where I'd push back: saying "I don't think it's effective" to lower SHBG is an opinion dressed as settled science. Some interventions do shift SHBG. Danazol, stanozolol, and certain androgens lower it measurably, though those carry real risks. Even lifestyle changes like weight loss and resistance training modestly reduce SHBG in obese men (Winters et al., 2014, Clinical Endocrinology). The creator is probably right that most online "SHBG hacks" are overhyped. But the blanket dismissal oversimplifies things.

They also didn't mention that elevated SHBG can be a symptom of something else worth investigating, like liver disease, hyperthyroidism, or anticonvulsant use. That's a missed clinical teaching moment.

What should you actually know?

SHBG is a clinically meaningful variable, not just a diagnostic checkbox. If your total testosterone looks normal but you're symptomatic, asking your provider to check both SHBG and free testosterone is a reasonable and evidence-backed request.

That said, the creator's skepticism about aggressively "optimizing" SHBG on TRT is defensible. There's no strong randomized controlled trial evidence showing that lowering SHBG in TRT patients improves outcomes like energy, libido, or body composition independently of free testosterone levels. Most of the enthusiasm for SHBG manipulation comes from bodybuilding forums, not peer-reviewed endocrinology.

If you're on TRT and your provider isn't checking free testosterone or SHBG at all, that's a conversation worth having. If you're healthy and someone is trying to sell you a supplement stack to "crush your SHBG," be skeptical. And if your SHBG is abnormally high or low, ask why, because it might point to something systemic that's worth addressing on its own terms.

• Normal SHBG range is roughly 10-57 nmol/L in adult men, though labs vary.
• SHBG rises with age, which is one reason older men often have lower free T even with acceptable total T.
• Obesity lowers SHBG, which can make total testosterone appear falsely low in overweight men.