Sex Hormone Binding Globulin

SHBG is a transport protein made primarily in the liver that binds tightly to sex hormones — mainly testosterone, dihydrotestosterone (DHT), and oestradiol (a form of oestrogen) — and carries them through the bloodstream.

Only unbound (“free”) testosterone can enter cells and exert its biological effects. SHBG acts like a “gatekeeper,” controlling how much of this active testosterone is accessible to tissues such as muscle, brain, and reproductive organs.

In men, roughly 60% of testosterone is bound to SHBG, 38% to albumin, and only 2% remains free and bioavailable. Because of this, SHBG levels directly influence total, free, and bioavailable testosterone balance.

Balanced SHBG is essential for hormonal homeostasis and overall male health.

• Low SHBG can lead to excess free testosterone, which may seem beneficial but often signals insulin resistance, metabolic syndrome, or obesity, and may contribute to acne or prostate issues.

• High SHBG binds too much testosterone, leaving less free hormone available — potentially leading to fatigue, low libido, muscle loss, depression, or reduced fertility.

• Emerging evidence also links abnormal SHBG levels to type 2 diabetes, cardiovascular disease, and liver dysfunction, making it both a hormonal and metabolic marker for men’s long-term health.

SHBG levels shift in response to diet, body composition, liver function, and hormonal environment.

Dietary Factors:

• Increases SHBG: High-protein, moderate-fat, low-glycemic diets; fibre-rich foods (e.g., legumes, leafy greens).

• Decreases SHBG: High sugar or refined carbohydrate intake; excessive alcohol consumption.

Lifestyle Factors:

• Regular exercise and healthy body weight raise SHBG.

• Obesity, sedentary behaviour, and chronic stress suppress it.
  

Related Biomarkers:

• High insulin and IGF-1 lower SHBG; improved insulin sensitivity raises it.

• Liver function markers (ALT, AST) and thyroid hormones (especially T3) also influence SHBG synthesis.
  

Micronutrient Impacts:

• Vitamin D, zinc, and magnesium support healthy SHBG production.
  

Environmental Influences:

• Exposure to endocrine-disrupting chemicals (EDCs) such as BPA or phthalates may alter SHBG levels by interfering with hepatic hormone regulation.

If SHBG is High

When SHBG is elevated, too much testosterone is bound, reducing the bioavailable fraction.

Diet

• Increase healthy fats (avocados, olive oil, wild salmon, nuts) to support androgen production.

• Include complex carbs (sweet potatoes, quinoa) to stabilise insulin and reduce SHBG overproduction.

• Avoid excessive alcohol and very low-calorie diets.
  

Lifestyle

• Focus on resistance training (3–4x/week) to boost free testosterone.

• Reduce chronic stress (which elevates cortisol and SHBG).

• Prioritise adequate sleep (7–9 hours) for hormonal regulation.
  

Supplements

• Zinc (15–30 mg/day): Supports testosterone synthesis and may lower elevated SHBG.

• Vitamin D (2,000–4,000 IU/day): Optimises androgen signalling and liver regulation of SHBG.

• Boron (3–6 mg/day): Shown in some studies to lower SHBG and increase free testosterone.
  

If SHBG Is Low

Low SHBG often reflects metabolic dysfunction, insulin resistance, or excess body fat.

Diet

• Emphasise whole-food, low-glycemic meals: vegetables, lean protein, healthy fats.

• Limit refined sugars, white flour, and processed foods to improve insulin sensitivity.

• Add omega-3 fatty acids (2–3 servings of fatty fish weekly or fish oil supplements) to support liver and metabolic function.
  

Lifestyle

• Incorporate daily movement (walking, strength training, HIIT).

• Achieve and maintain healthy body composition.

• Avoid smoking and minimise alcohol intake, which can further suppress SHBG.
  

Supplements

• Omega-3 fatty acids (1–3 g EPA+DHA/day): Improve insulin sensitivity and SHBG.

• Vitamin D (2,000–4,000 IU/day): Supports liver function and SHBG synthesis.

1. Basualto-Alarcón, C., Llanos, P., García-Rivas, G., et al. (2021). Classic and Novel Sex Hormone Binding Globulin Effects on the Cardiovascular System in Men. International Journal of Endocrinology, 2021:5527973. https://doi.org/10.1155/2021/5527973
   

2. Thaler, M. A., Seifert-Klauss, V., & Luppa, P. B. (2015). The Biomarker Sex Hormone-Binding Globulin: From Established Applications to Emerging Trends in Clinical Medicine. Best Practice & Research Clinical Endocrinology & Metabolism, 29(5), 749–760. https://doi.org/10.1016/j.beem.2015.06.005
   

3. Brianso-Llort, L., Saéz-Lopez, C., Alvarez-Guaita, A., et al. (2024). Recent Advances on Sex Hormone-Binding Globulin Regulation by Nutritional Factors: Clinical Implications. Molecular Nutrition & Food Research, 68(14), e2400020. https://doi.org/10.1002/mnfr.202400020
   

4. Gyawali, P., Martin, S. A., Heilbronn, L. K., et al. (2018). Cross-Sectional and Longitudinal Determinants of Serum Sex Hormone Binding Globulin (SHBG) in a Cohort of Community-Dwelling Men. PLoS ONE, 13(7), e0200078. https://doi.org/10.1371/journal.pone.0200078
   

5. Yeap, B. B., Marriott, R. J., Antonio, L., et al. (2021). Sociodemographic, Lifestyle and Medical Influences on Serum Testosterone and Sex Hormone-Binding Globulin in Men From UK Biobank. Clinical Endocrinology, 94(2), 290–302. https://doi.org/10.1111/cen.14342