Quick answer: SHBG (sex hormone-binding globulin) is a protein made by the liver that binds testosterone and estrogen, controlling how much is free and active. Low SHBG, often linked with insulin resistance and excess weight, raises free hormones and is common in PCOS. High SHBG lowers free testosterone and can occur with aging, hyperthyroidism, low-calorie diets or estrogen therapy.
Key takeaways
SHBG is a liver protein that binds testosterone and estrogen and controls how much is free and active.
Low SHBG often travels with insulin resistance and extra weight and is common in PCOS.
High SHBG lowers free testosterone and can occur with aging, an overactive thyroid, very low-calorie diets or estrogen therapy.
What is SHBG?
SHBG is a liver protein that carries sex hormones in the blood. Hormones bound to SHBG are inactive; only the free portion acts on tissues.
Why SHBG matters
SHBG controls free testosterone and estrogen, helps interpret total testosterone, and reflects insulin and liver health.
Understanding your result
Reference ranges vary by lab, age and sex. Your provider interprets your result against the lab’s range and your overall picture, rather than chasing a single number. Functional labs are optional. They can be helpful in more complex cases.
What low SHBG can mean
Low SHBG can reflect insulin resistance and type 2 diabetes, excess weight, or PCOS. Hypothyroidism and androgen or steroid use can also lower it.
What high SHBG can mean
High SHBG can reflect aging (especially in men), hyperthyroidism, or estrogen therapy or birth control. Liver disease and very low-calorie or low-protein diets can also raise it.
What affects SHBG
SHBG is affected by insulin levels, thyroid function, body weight, estrogen exposure, and liver health.
Ways to support healthy levels
Improve insulin sensitivity to raise low SHBG (see insulin sensitivity), check thyroid function, and eat enough protein and calories. Interpret it with total and free testosterone.
What does the research show about SHBG?
A nested case-control study in the Women’s Health Study compared 359 postmenopausal women who developed type 2 diabetes with 359 who did not. Women in the highest quarter of SHBG had about 91% lower odds of diabetes than those in the lowest quarter (odds ratio 0.09), a result repeated in 340 men from the Physicians’ Health Study II (odds ratio 0.10), and gene variants that raise SHBG were linked with lower risk. Case-control designs measure SHBG once and can still be affected by factors the researchers did not capture. (Ding et al., 2009)
In the UK Biobank, researchers followed 149,436 men aged 40 to 69 for about 11 years, during which 10,053 died. Men in the lowest fifth of testosterone had a 14% higher death rate than those in the highest fifth (hazard ratio 1.14), and calculated free testosterone showed similar results, while men with the lowest SHBG had a 32% lower death rate than those with the highest (hazard ratio 0.68). Testosterone was measured once by immunoassay, and observational data cannot show that changing these levels would change risk. (Yeap et al., 2021)
These studies suggest that low SHBG often travels with insulin resistance, while high SHBG in older men tracks with higher mortality, so SHBG is best read with testosterone, insulin and liver and thyroid markers.
SHBG and healthy aging
SHBG reflects metabolic health: low levels are linked with insulin resistance, while high levels in older men can reduce active testosterone, which is linked with changes in muscle and energy.
When to see a naturopathic doctor
It may be time to see a naturopathic doctor if you have symptoms of low testosterone with normal total testosterone, or signs of PCOS. The same is true if you have insulin resistance or thyroid concerns.
SHBG at a glance
| Topic | What the article explains |
|---|---|
| Why it matters | Controls free testosterone and estrogen; helps interpret total testosterone; and reflects insulin and liver health |
| What can affect it | Insulin levels; thyroid function; body weight; estrogen exposure; and liver health |
| Supportive habits discussed | Improve insulin sensitivity to raise low SHBG; check thyroid function; eat enough protein and calories; and interpret with total and free testosterone |
Questions to bring to your clinician
These questions can help you get the most out of your next visit.
Could insulin resistance or my diet be shifting my SHBG level?
What might my SHBG be telling us, given my health history and symptoms?
Which other labs would be worth pairing with my SHBG to get a clearer picture?
When would it make sense to recheck my SHBG, and what could I work on in the meantime?
Frequently asked questions
What does low SHBG mean?
It often reflects insulin resistance and is common in PCOS.
What does high SHBG mean?
It lowers free testosterone and can occur with aging, hyperthyroidism or estrogen use.
How can I raise SHBG naturally?
Improving insulin sensitivity and losing excess weight often raises SHBG.
Why test SHBG with testosterone?
It helps estimate how much testosterone is actually free and active.
Sources
- Bhasin S, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab 2018. PMID: 29562364. https://pubmed.ncbi.nlm.nih.gov/29562364/
- Ding EL, et al. Sex hormone-binding globulin and risk of type 2 diabetes in women and men. N Engl J Med 2009. PMID: 19657112. https://pubmed.ncbi.nlm.nih.gov/19657112/
- Teede HJ, et al. Recommendations From the 2023 International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome. J Clin Endocrinol Metab 2023. PMID: 37580314. https://pubmed.ncbi.nlm.nih.gov/37580314/
- Vermeulen A, et al. A critical evaluation of simple methods for the estimation of free testosterone in serum. J Clin Endocrinol Metab 1999. PMID: 10523012. https://pubmed.ncbi.nlm.nih.gov/10523012/
- Yeap BB, et al. Serum Testosterone is Inversely and Sex Hormone-binding Globulin is Directly Associated with All-cause Mortality in Men. J Clin Endocrinol Metab 2021. PMID: 33059368. https://pubmed.ncbi.nlm.nih.gov/33059368/
- MedlinePlus: SHBG Blood Test
- MedlinePlus: Testosterone Levels Test
This article is for educational purposes only and is not medical advice. It does not replace an individual evaluation. Talk with your healthcare provider before starting supplements or changing medications, especially if you are pregnant, nursing, or managing a health condition.
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