Sex Hormone Binding Globulin (SHBG)

The Sex Hormone Binding Globulin (SHBG) test measures the amount of SHBG in the blood. SHBG is a protein produced by the liver that binds to sex hormones—primarily testosterone and estrogen—and regulates their bioavailability. This test is often used in evaluating hormonal imbalances, particularly related to testosterone in both men and women.

1. What Is SHBG?

• SHBG is a glycoprotein that binds tightly to sex hormones such as testosterone and estrogen.

• It controls how much of these hormones are freely available to tissues (free vs. bound hormone).

• Only unbound (free) hormones are biologically active, so SHBG levels affect overall hormone activity.

2. Why Is the SHBG Test Performed?

This test is used to:

• Evaluate symptoms of hormone imbalance (e.g., fatigue, infertility, low libido, irregular periods).

• Diagnose conditions such as polycystic ovary syndrome (PCOS), androgen deficiency, or estrogen excess.

• Help determine free testosterone levels when total testosterone results are inconclusive.

• Monitor liver function, as SHBG is produced in the liver.

3. SHBG Reference Ranges

• Men: 10 – 57 nmol/L

• Women: 18 – 144 nmol/L

• Levels vary depending on age, sex, liver function, and hormone status.

4. Interpreting SHBG Results

🔹 High SHBG:

• May result in lower free testosterone levels (even if total testosterone is normal).

• Common in hyperthyroidism, liver disease, estrogen therapy, and anorexia.

🔹 Low SHBG:

• May lead to higher free testosterone levels.

• Seen in insulin resistance, obesity, PCOS, hypothyroidism, and androgen use.

5. What Can Affect SHBG Levels?

• Liver health and function

• Thyroid status (high in hyperthyroidism, low in hypothyroidism)

• Hormonal therapies (e.g., estrogen or testosterone supplementation)

• Metabolic disorders such as obesity, diabetes, or PCOS

6. How Is the Test Performed?

• A blood sample is taken from a vein.

• Fasting may or may not be required—follow your provider's instructions.

7. When to See a Doctor

🚨 Speak with your healthcare provider if you:

• Have symptoms of low testosterone or estrogen imbalance.

• Experience unexplained infertility, weight changes, or changes in sexual function.

• Have abnormal hormone levels and need a deeper evaluation.

🔹 Key Takeaways

✅ SHBG controls the amount of active sex hormones in the body.

✅ Abnormal levels can disrupt hormone balance and reproductive function.

✅ SHBG testing helps provide a clearer picture when hormone-related symptoms are present.