What is SHBG?
Only unbound (free) hormones can readily enter cells and activate hormone receptors. Because of this, SHBG plays a major role in determining androgen and estrogen activity throughout the body. Even when total hormone levels appear normal, abnormal SHBG levels can significantly alter hormone bioavailability and contribute to symptoms of hormonal imbalance.
SHBG production is influenced by numerous physiological factors, including insulin levels, liver function, thyroid status, inflammation, body composition, age, and overall metabolic health.
Why Test for SHBG?
Evaluating SHBG levels helps clinicians better understand hormone availability and investigate symptoms related to androgen or estrogen imbalance, such as:
• Erectile dysfunction or reduced sexual function
• Hair loss, acne, or androgen excess symptoms
• Irregular menstrual cycles or infertility
• PCOS and insulin resistance
• Obesity or metabolic syndrome
• Thyroid dysfunction
• Monitoring hormone replacement therapy or testosterone therapy
SHBG is particularly valuable because total testosterone alone may not accurately reflect hormone activity. Two individuals with identical testosterone levels can have very different free testosterone levels depending on SHBG concentration.
Clinical Significance of SHBG Levels
- Low SHBG Levels: SHBG levels below ~20 nmol/L are commonly associated with insulin resistance, obesity, metabolic syndrome, hypothyroidism, fatty liver disease, chronic inflammation, or elevated androgen states. Lower SHBG increases the amount of free testosterone and free estradiol circulating in the body. Clinically, low SHBG may contribute to acne, androgenic hair loss, PCOS-related symptoms, irritability, and metabolic dysfunction. Persistently low SHBG is also considered an early marker of cardiometabolic risk and impaired insulin sensitivity.
- High SHBG Levels: SHBG levels above ~70–80 nmol/L may occur with hyperthyroidism, liver disease, aging, calorie restriction, low insulin states, oral estrogen therapy, or reduced androgen production. Elevated SHBG reduces free testosterone availability even when total testosterone appears normal. Clinically, high SHBG is often associated with fatigue, low libido, reduced muscle mass, poor exercise recovery, erectile dysfunction, menstrual irregularities, or symptoms of androgen deficiency.
Actionable Insights
Insulin resistance is one of the most common drivers of low SHBG, making SHBG a useful indirect marker of metabolic health. Liver function, thyroid status, inflammation, nutritional status, medications, and hormone therapies can all significantly alter SHBG production. Monitoring trends over time may provide better clinical insight than isolated measurements.
Optimal Ranges
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Men: ~20–50 nmol/L
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Women (Premenopausal): ~40–120 nmol/L
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Women (Postmenopausal): Often lower than premenopausal ranges
Note: Reference ranges vary by laboratory. In functional medicine, some providers may consider a narrower interpretive window to help guide clinical context. These values are not standardized and should be interpreted in conjunction with the ordering provider’s judgment.
“SHBG serves as a valuable indirect marker of metabolic and endocrine health. With patients on hormone therapies or with discrepant symptoms, measuring SHBG alongside free testosterone calculations helps avoid misinterpreting bioavailability, supporting more precise, individualized management while considering broader factors like thyroid status and liver function. Free Androgen Index (FAI): FAI = 100 × (Total Testosterone [nmol/L] ÷ SHBG [nmol/L]) Men generally targeting 30–100+ and women <5–7 depending on lab/age. men generally targeting 30–100+ and women <5–7 depending on lab/age.”
Dr. Mitch Ghen - Director of Physician Consultations, Access Labs
Disclaimer: Content on the Access Labs blog is for informational purposes only and reflects the views of individual contributors, not necessarily those of Access Labs. We do not endorse specific treatments, products, or protocols. This content is not a substitute for professional medical advice. Always consult a qualified healthcare provider regarding any medical concerns.
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Access is the nation’s premier specialty diagnostic lab. We offer a broad menu of testing from blood, saliva, urine & swab samples. We perform all of your tests in our 25,000 sq. ft. ultra-automated facility in Jupiter, Florida & provide results within 24hrs. Since 2003, we continuously strive to innovate, inspire, and improve solutions for physicians by providing an exceptional personalized experience with the most accurate testing.
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