SHBG: The Hormone Availability Regulator

SHBG is produced by hepatocytes and regulated by multiple factors. Insulin suppresses SHBG production, which is why insulin-resistant individuals typically have low SHBG. Thyroid hormones and estrogens increase SHBG production. Only hormones not bound to SHBG (free hormones) can enter cells and exert biological effects. When SHBG is low, more testosterone and estradiol are free, which can cause androgen excess symptoms in women (acne, hirsutism, PCOS) and estrogen excess in men. When SHBG is high, less hormone is bioavailable, potentially causing symptoms of deficiency despite normal total hormone levels.

1

Insulin Resistance Connection

Low SHBG is one of the strongest biomarkers for insulin resistance. It often declines before fasting insulin or glucose becomes abnormal.

2

Context for Total Testosterone

Total testosterone is meaningless without knowing SHBG. A man with total testosterone of 500 ng/dL and high SHBG may have less free testosterone than a man with 400 ng/dL and normal SHBG.

Optimal SHBG Benchmarks

Functional Range (Hormonal Focused) Men optimal: 20-50 nmol/L; Women optimal: 40-120 nmol/L
Standard Lab Range Standard: Men 10-57 nmol/L; Women 18-144 nmol/L

Common Questions

Why is SHBG important?

SHBG determines what percentage of your total testosterone and estradiol is biologically active. Without knowing SHBG, total hormone levels can be misleading.

What causes low SHBG?

Insulin resistance is the most common cause of low SHBG. Obesity, type 2 diabetes, PCOS, and metabolic syndrome all lower SHBG through hyperinsulinemia.