SHBG as a PCOS marker: what the evidence actually supports

What's this video probably claiming?

Based on the caption and creator context, @pcosnikki is likely making the case that sex hormone-binding globulin (SHBG) is an underutilized biomarker in PCOS diagnosis and management, and that viewers should be requesting this test from their doctors. Coaches in the PCOS space frequently frame low SHBG as a standalone red flag, something that confirms androgen excess or insulin resistance even when standard diagnostic criteria haven't been met. The video probably encourages followers to "know their number," implying a specific threshold separates health from hormonal dysfunction. There may also be suggestions that dietary changes, supplements like inositol, or lifestyle interventions can raise SHBG levels. These are not inherently wrong positions, but the framing matters enormously. SHBG is a real and clinically relevant marker, but treating it as a diagnostic anchor for PCOS, separate from the Rotterdam criteria, is a meaningful oversimplification that could send people chasing a number rather than getting proper clinical evaluation.

What does the science actually show?

SHBG is a glycoprotein produced primarily in the liver that binds testosterone and estradiol, regulating their bioavailability. In women with PCOS, SHBG is frequently low, which elevates free androgen levels even when total testosterone appears normal. A 2010 study by Goodarzi et al. in the Journal of Clinical Endocrinology and Metabolism confirmed that low SHBG is associated with hyperandrogenism and insulin resistance in PCOS populations. Insulin directly suppresses hepatic SHBG production, so women with metabolic dysfunction tend to have the lowest levels. Reference ranges typically sit between 18 and 144 nmol/L for premenopausal women, but that range is wide enough to be clinically frustrating. A 2013 systematic review by Ding et al. in Diabetes Care found that each 1 nmol/L increase in SHBG was associated with a 1.3% lower risk of type 2 diabetes, reinforcing its role as a metabolic signal, not just a sex hormone shuttle. Importantly, SHBG is not part of the Rotterdam criteria used to diagnose PCOS, and no major guideline currently lists it as a required diagnostic test.

Where does the social media noise diverge from clinical reality?

The biggest problem with SHBG content in the PCOS creator space is the leap from "low SHBG is associated with PCOS" to "low SHBG means you have PCOS" or "fixing your SHBG fixes your PCOS." Those are not the same claims. SHBG is a downstream marker influenced by insulin, thyroid function, liver health, obesity, and even certain medications including oral contraceptives, which can dramatically raise SHBG. A woman coming off the pill may see artificially elevated SHBG that normalizes over months, which can be misread as improvement or decline depending on timing. Additionally, some creators in this space suggest that a low-normal SHBG reading alone justifies concern without any of the three Rotterdam criteria being present. A 2018 paper by Teede et al. in Human Reproduction, which produced the international evidence-based PCOS guideline, explicitly notes SHBG as a supportive, not diagnostic, tool. Coaches are not licensed to order labs or interpret them in a clinical context, and framing SHBG as "your PCOS marker" without that caveat is where this content edges toward misleading.

What should you actually know?

SHBG is worth discussing with your doctor if you have PCOS or suspect you might, but it functions best as one piece of a larger hormonal panel, not a standalone verdict. Clinically useful companion tests include free and total testosterone, DHEA-S, fasting insulin, fasting glucose, and a full thyroid panel. If your SHBG is low, that is a signal worth investigating, particularly alongside fasting insulin levels, since hyperinsulinemia is one of the most direct suppressors of hepatic SHBG production. Research by Nestler et al. in the New England Journal of Medicine (1991) showed that reducing insulin levels with metformin raised SHBG in women with PCOS, which supports the mechanistic link. Inositol supplementation, specifically the myo-inositol and D-chiro-inositol combination studied by Unfer et al. (2017, Gynecological Endocrinology), has shown modest improvements in insulin sensitivity and androgen profiles in PCOS, which could indirectly affect SHBG. The key word is indirectly. None of this replaces a diagnosis from a qualified clinician using validated criteria.