Summary

Sex Hormone-Binding Globulin (SHBG) is a vital protein produced by the liver, which plays a central role in controlling the amount of sex hormones your body can use. By binding to the hormones, including testosterone and estrogen, SHBG helps to regulate their bioavailability in the body's cells.

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Overview

The primary function of SHBG is to transport sex hormones in the bloodstream. Knowing that sex hormones are hydrophobic molecules, unable to transport itself through the body all alone, it emphasizes its importance in the human body. It binds tightly to testosterone and estrogen, the two main sex hormones, rendering them inactive. Only the unbound hormones, or 'free' hormones, can affect the body by entering cells and influence the transcription of genes in the nucleus. Consequently, SHBG can indirectly influence various physiological processes due to its role in determining the levels of active sex hormones.^[1,4]

An SHBG test is usually done if you experience symptoms and/or signs of having too little or too much testosterone. It is a ‘’male’’ sex hormone produced primarily by testes, although females also have small amounts of it produced by the ovaries and adrenal glands. 

This test can assist in diagnosing men with symptoms of low testosterone, such as low libido, erectile dysfunction, infertility, mood changes, and loss of muscle mass. It can also be used for diagnosing women, experiencing symptoms of high testosterone, like irregular menstruation, acne, weight gain, excessive hair growth, and infertility. 

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What should you know about this biomarker?

Each laboratory uses different machines and protocols, so the results might vary in terms of the reference ranges or used units of measurement. In Macromo blood tests, we use nmol/l (nanomoles per liter).

The optimal range for SHBG levels typically falls between 14.5 to 48.4 nmol/l for males and 19.8 to 155.2 nmol/l for females. However, it may decrease with age, obesity, insulin resistance, and certain medications. Low SHBG levels in men may be associated with conditions such as hypogonadism (low testosterone) and metabolic syndrome. In women, high SHBG levels may be related to conditions such as polycystic ovary syndrome (PCOS), while low levels may be associated with menopause and hormonal imbalances.^[2]

There are three possible states of your blood test result: low, average, and high levels.

• SHBG levels lower than the reference range could affect your hormonal balance, meaning your total testosterone is more available to use. Low levels of SHBG may be related to hypothyroidism, type 2 diabetes, obesity, Cushing’s syndrome, or polycystic ovary disease. However, it is normal for SHBG levels to decrease with age. Please consult your healthcare provider for further evaluation and potential treatment strategies.
• SHBG levels within the reference range are generally a good sign. However, regular check-ups are recommended.
• Elevated SHBG levels could impact your hormone levels, leading to a lower portion of readily available testosterone. High SHBG levels can be associated with liver disease, hyperthyroidism, eating disorders, oral contraception, etc. Consult your healthcare provider for a detailed understanding and potential next steps. 

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Genetics

Genetics also plays a role in determining SHBG levels. Various genetic variants have been linked with changes in SHBG concentrations, indicating a heritable component to this biomarker. 

However, lifestyle and environmental influences can also significantly impact SHBG levels, adding another layer of complexity to this biomarker.^[1,3]  ‍
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Recommendations

If your results of SHBG are not within the optimal range, it is important to find out the cause:

• If your SHBG levels are not in the reference range, it's essential to consult with a healthcare provider.
• Lifestyle modifications such as maintaining a healthy weight, eating a balanced diet, engaging in regular physical activity, and limiting alcohol intake may help manage SHBG levels. 
• If the SHBG levels are significantly out of the normal range and there might be a suspected genetic component, you can consider undergoing DNA testing.

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The information and tests provided on our website are for educational purposes only and are not a substitute for professional medical advice. Always consult with your healthcare provider before making health decisions. Our tests do not diagnose or treat diseases. Individual results may vary and should be discussed with a healthcare provider.