SHBG and testosterone: is the ratio really that simple?

What did @doc.jona actually say?

Honestly? Very little that's usable. The transcript is almost entirely incoherent, likely the result of a failed auto-transcription of a German-language video. Phrases like "the S.H.B.E.S.S. is very unique" and "I am very glad to be here with the crew" tell us nothing about the actual medical claims. The caption, though, is clear: SHBG is "just as important" as testosterone. That's the claim we can evaluate, even if the transcript won't cooperate.

To be fair to @doc.jona, the caption framing is a reasonable position that practicing endocrinologists and TRT clinicians do take seriously. The hashtags suggest this is aimed at people considering or already on testosterone replacement therapy, which makes the topic genuinely relevant. But since we can't quote the creator directly on specifics, this fact-check will focus on what the science actually says about SHBG's clinical role.

Does the science back up the core claim?

Yes, with some important nuance. SHBG absolutely affects how much testosterone your body can actually use, and ignoring it leads to clinical errors. But "just as important" is a simplification that could mislead people into over-interpreting a single number.

SHBG, or sex hormone-binding globulin, binds tightly to testosterone in the bloodstream. Only the unbound fraction, called free testosterone, can enter cells and activate androgen receptors. A man with total testosterone of 600 ng/dL and very high SHBG might have less biologically active hormone than a man with 400 ng/dL and low SHBG. Rosner et al. (2007, Journal of Clinical Endocrinology and Metabolism) showed that calculated free testosterone using SHBG correlates better with symptomatic hypogonadism than total testosterone alone. Cawley et al. (2020, European Journal of Endocrinology) reinforced this, finding that free androgen index and calculated free testosterone improved diagnostic accuracy in men with borderline total T levels. The science does support measuring SHBG. Whether it is equally important or differently important depends on the clinical picture.

What did they get wrong, or right?

The caption claim holds up reasonably well in clinical practice, even if "just as important" is a bit of a marketing simplification. What's right: SHBG is routinely underordered, and many patients on TRT or investigating low T symptoms get only a total testosterone number. That incomplete picture causes real diagnostic mistakes.

What's potentially misleading: framing SHBG as equally important to testosterone in all cases could encourage people to obsess over SHBG optimization independent of symptoms. Some men have naturally elevated SHBG due to genetics, thyroid status, or liver health, and chasing a "better" SHBG number without addressing the root cause is the wrong approach. Also, SHBG levels shift with age, obesity, insulin resistance, and alcohol use. Morgentaler and Traish (2009, European Urology) argued that free testosterone calculation has real limits because SHBG assays vary between labs. So the number isn't as clean or comparable as a caption makes it sound. Credit where it's due: the general message that one number is not enough is correct and worth spreading.

What should you actually know?

If you're getting bloodwork done for testosterone-related symptoms, you need total testosterone, free testosterone, and SHBG together. One without the others leaves you guessing.

Here's what matters clinically. SHBG rises with age, which partly explains why older men feel symptoms of low T even when their total testosterone looks normal on paper. Obesity and insulin resistance tend to lower SHBG, which can mask genuinely low total testosterone by inflating the free fraction. Liver disease raises SHBG significantly. Thyroid dysfunction changes it. These aren't minor footnotes. They change clinical decisions. Bhasin et al. (2010, Journal of Clinical Endocrinology and Metabolism) in the Endocrine Society's clinical practice guidelines explicitly recommend measuring SHBG in men with conditions that affect SHBG concentrations before concluding someone is or isn't hypogonadal. If a telehealth platform or doctor is making TRT decisions based only on total testosterone, that's a problem. The caption's underlying message, that SHBG belongs in the conversation, is clinically defensible. Just don't treat a single SHBG reading as a verdict.