SHBG (Sex hormone-binding globulin)
The protein that decides how much of your testosterone is actually free to act.
What it is
SHBG is a liver-produced glycoprotein that binds sex hormones — primarily testosterone, dihydrotestosterone and oestradiol — and reduces their bioavailability. It is the single biggest reason that a normal-looking total-T result can still leave a man symptomatic.
Why it matters
Without SHBG, free-T calculations are guesswork. Conditions that raise SHBG (hyperthyroidism, advanced age, low calorie intake, alcohol-related liver changes) can mask an underlying testosterone problem. Conditions that lower SHBG (insulin resistance, obesity, hypothyroidism, high androgen exposure) can make a borderline-low total-T look bioavailable when it is actually adequate.
Adult male reference range
Adult male reference range is roughly 18–54 nmol/L.
Role on the panel
On the Hormone Panel 01, SHBG is the bridge between total testosterone and the free fraction. It is also a metabolic-health surrogate: very low SHBG correlates strongly with insulin resistance and metabolic syndrome.
When it reads low
Low SHBG suggests insulin resistance, obesity, hypothyroidism, or exogenous androgen use. A low value warrants a metabolic check.
When it reads high
High SHBG can be driven by hyperthyroidism, ageing, anti-androgens, or oestrogen-dominant states. It often explains why a normal total-T is paired with low-T symptoms.
Common questions about this marker.
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