SHBG: What It Is and What Your Test Result Means

What Is SHBG

SHBG (Sex Hormone-Binding Globulin) is a protein produced by the liver that circulates in the blood. Its primary function is to bind sex hormones: testosterone, estrogen, and dihydrotestosterone. Bound hormones are biologically inactive — they are held, so to speak, in reserve. Only the free, unbound fraction of hormones can act on cells and tissues. This means that SHBG directly determines how much active testosterone or estrogen reaches your tissues, even if the total hormone level in your blood appears normal. For this reason, SHBG is often measured alongside total testosterone to evaluate the true, biologically available hormone level.

Reference Ranges

SHBG is measured in nmol/L. Reference ranges differ by sex:

• Men: 16.5–55.9 nmol/L
• Women: 24.6–122.0 nmol/L

The wider range in women reflects natural hormonal fluctuations across the menstrual cycle, during pregnancy, and around menopause. In older men, SHBG typically rises, so results should always be interpreted in the context of age.

Why SHBG May Be High

Elevated SHBG means that more hormones are bound, leaving less in a free, active form. Common causes:

• Liver disease: the liver produces SHBG, and certain liver conditions can increase its output.
• Hypothyroidism: reduced thyroid function is often associated with higher SHBG.
• Older age: SHBG rises naturally with age, especially in men.
• Low body weight or intense fasting: inadequate nutrition stimulates SHBG production.
• Estrogen use: oral contraceptives or hormone replacement therapy can significantly raise SHBG.
• Alcohol consumption: chronic alcohol use is associated with higher SHBG.

Why SHBG May Be Low

Low SHBG means that more hormones circulate in free form. This may sound beneficial, but it sometimes signals metabolic problems:

• Obesity and insulin resistance: one of the most common causes — insulin suppresses SHBG production in the liver.
• Type 2 diabetes: elevated insulin levels reduce SHBG.
• Hypothyroidism (in some cases): thyroid disorders can influence SHBG in either direction.
• Androgen excess: very high testosterone (or anabolic steroid use) suppresses SHBG.
• Polycystic ovary syndrome (PCOS): women with PCOS often have lower SHBG.

What to Do Next

If your SHBG falls outside the reference range, start by considering the broader picture. A single marker rarely tells the whole story. Lifestyle changes that may help normalize SHBG:

• Maintain a healthy body weight — obesity is one of the most powerful SHBG-lowering factors.
• Regular physical activity improves insulin sensitivity and may help normalize SHBG.
• A diet rich in fiber and low in ultra-processed foods supports liver health.
• Reduce alcohol consumption.

Discuss with your doctor whether further testing of thyroid function, liver markers, or insulin levels is warranted.

Monitoring Over Time

SHBG is a marker that changes slowly — it does not respond to daily fluctuations the way cortisol or glucose do. This means a single measurement is a solid baseline, but the real value comes from tracking trends over months or years. If you are changing your diet, managing your weight, or starting hormone therapy, checking SHBG every 3–6 months provides an objective picture of how your body is responding.

Questions to Ask Your Doctor

1. Does my SHBG level affect my free testosterone, and is it worth calculating? 2. What are the most likely causes of my SHBG abnormality — are there signs pointing to liver or thyroid problems? 3. Can lifestyle changes realistically shift my SHBG within the next 6 months? 4. When should I retest to check whether there has been any change?

*This is not medical advice. Consult your doctor before making any decisions about your health.*