SHBG — Sex Hormone Binding Globulin
SHBG determines how much of your testosterone and estradiol is biologically active. Low SHBG often signals insulin resistance; high SHBG can mask low free testosterone even when total testosterone appears normal.
SHBG (sex hormone-binding globulin) determines how much of your testosterone and estradiol is biologically active — low SHBG often signals insulin resistance, while high SHBG can mask low free testosterone even when total testosterone appears normal.
The biomarker
- Name: Sex Hormone-Binding Globulin (SHBG)
- Units: nmol/L
- Standard reference range: 10–80 nmol/L (men); 18–144 nmol/L (women)
- Optimal range: 20–60 nmol/L (men); 30–90 nmol/L (women)
How to read your result
| Value | Interpretation |
|---|---|
| < 20 nmol/L (men) / < 30 nmol/L (women) | Low — investigate insulin resistance, obesity, or hypothyroidism; more testosterone is free but context matters |
| 20–60 nmol/L (men) / 30–90 nmol/L (women) | Optimal — free testosterone can be interpreted meaningfully from total |
| > 60 nmol/L (men) / > 90 nmol/L (women) | High — may bind much of total testosterone, masking effective low free T; order free testosterone alongside |
What moves the needle
- Insulin resistance and obesity. Elevated insulin suppresses SHBG production in the liver — the most common cause of low SHBG in the general population. Improving insulin sensitivity through diet, exercise, and weight loss reliably raises SHBG toward the optimal range.
- Thyroid function. Hypothyroidism lowers SHBG; hyperthyroidism raises it. If SHBG is persistently abnormal without an obvious metabolic cause, check TSH + free T3/T4.
- Diet composition. High dietary fibre and moderate protein support normal SHBG. High simple-sugar diets that drive insulin spikes tend to suppress SHBG over time.
- Body composition. Excess adipose tissue increases oestrogen (via aromatase) and reduces SHBG in men. Resistance training and fat loss generally move SHBG toward the optimal range.
Why this test is worth asking for
- Total testosterone alone is an incomplete picture — two people with identical total testosterone but very different SHBG have very different biologically active hormone levels.
- Low SHBG is an early, reversible signal of insulin resistance that often appears before fasting glucose or HbA1c become abnormal.
- High SHBG can explain symptoms of low testosterone (fatigue, low libido, slow recovery) even when total testosterone reads in the normal range — ordering free testosterone alongside SHBG resolves the ambiguity.
- SHBG is inexpensive and pairs naturally with testosterone on any hormonal panel.
Related protocols
- Testosterone — Total + Free (Men)
- Fasting Insulin + HOMA-IR — Insulin Sensitivity
- TSH + Free T3/T4 — Thyroid Panel
Sources
AgeGen lab guides are educational only. We do not provide medical diagnosis, prescribe brands, or recommend specific doses. Talk to a licensed clinician before changing your supplement or medication routine.