Understanding SHBG: Normal vs Optimal Ranges

?What is SHBG?

Sex hormone binding globulin (SHBG) is a protein produced by the liver that binds tightly to testosterone and oestradiol, making them biologically inactive. High SHBG means more testosterone is bound and less is free to act on cells — even if total testosterone appears normal.

!Why It Matters

SHBG is the key modulator of free testosterone levels. High SHBG (more common with ageing, hypothyroidism, liver disease, and oestrogen exposure) reduces free testosterone. Low SHBG (from obesity, insulin resistance, hypothyroidism) can increase free testosterone but is associated with higher risk of type 2 diabetes. SHBG is also an independent predictor of metabolic syndrome.

Reference Ranges

Lab normal ranges may vary between laboratories. Optimal and longevity targets are based on research literature and should be interpreted with your physician.

Symptoms of Imbalance

• High SHBG: symptoms of low free testosterone despite normal total testosterone
• Low SHBG: associated with metabolic syndrome, insulin resistance

How to Improve Your Levels

• 1High SHBG: treat hypothyroidism; reduce alcohol and estrogenic exposures
• 2Low SHBG: improve insulin sensitivity through diet, exercise, and weight loss

When to Test

Order alongside total testosterone when evaluating testosterone status or metabolic syndrome.

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