Hormone levels play a very important role in your health, and your body is constantly using different mechanisms to keep your hormones within a normal range. When your hormone levels are too low or too high, you can develop a wide range of symptoms and manifestations that can affect your wellbeing.

Sex hormone-binding globulin is one of these mechanisms. Keep reading to learn more about sex hormone-binding globulin, its functions, and what your normal test results should be.

What is sex hormone-binding globulin (SHBG)?

Sex hormone-binding globulin, or SHBG, is a type of protein that is produced in your liver. According to the University of Rochester Medical Center, SHBG is produced by both men and women and it binds to three different sex hormones, which are:

Estrogen
Dihydrotestosterone (DHT)
Testosterone

After it binds to these hormones, SHBG is able to carry them throughout your bloodstream. But when hormones are bound to SHBG, they can’t be used by your tissues. That’s why SHBG levels are a mechanism that helps regulate sex hormone levels in your body, especially testosterone levels.

Testosterone is the main sex hormone in men, but it’s also important in female health. Having low testosterone levels can cause problems for men, while high testosterone levels can affect women.

What is a SHBG blood test?

As its name suggests, a SHBG blood test can be used to measure the levels of SHBG circulating in your bloodstream.

In men, approximately 45-65% of testosterone in the blood is bound to SHBG, while 66-78% of testosterone in women is bound to this protein. As a result, a SHBG test is a good indicator of how much testosterone is in your blood and how much is going to your tissues.

The test is performed using a sample of venous blood, which is collected with a needle. You don’t need to do anything special to prepare for a SHBG blood test. However, you should inform your doctor about any medications or supplements you’re currently taking, since some substances can alter your hormone levels or test results.

Biotin supplements are known to affect sex hormone-binding globulin normal levels. If you’re taking biotin, you should wait at least 8 hours after taking the supplement before getting this test.

Sex hormone-binding globulin test results are typically ready within 1-3 days. You should always discuss SHBG results and other test results with your healthcare provider so you understand what your results mean, and how to take care of your health.

Sex hormone binding globulin female levels

Sex hormone binding globulin ranges for women between the ages of 18-46 are 18.2-135.5 nmol/L. SHBG normal test results for postmenopausal women are 16.8-125.2 nmol/L.

Sex hormone binding globulin male levels

For adult men, normal SHBG test results range between 13.3-89.5 nmol/L.

Who needs a SHBG test?

Your healthcare provider could ask for a SHBG test if they suspect that you have abnormal testosterone levels, especially if total testosterone test results don’t explain your symptoms.

According to MedlinePlus, this test can help determine just how much testosterone is actually going to your tissues in order to be used by your body. A total testosterone test, on the other hand, can determine how much testosterone is in your body, but not how much testosterone is available for use.

In most cases, men who get a SHBG test have symptoms of low testosterone. Women who need this test typically have signs of high testosterone levels.

According to Mayo Clinic Laboratories, SHBG testing can also be useful for:

Monitoring hormone therapy
Diagnosing puberty disorders
Diagnosing and managing eating disorders
Diagnosing thyrotoxicosis
Diagnosing and monitoring diabetes and heart disease

Causes of low SHBG

Low SHBG levels could mean that the protein isn’t binding itself to enough testosterone. This means that more testosterone is going to your tissues, which could lead to high testosterone symptoms.

According to the NHS Foundation Trust, some causes of low SHBG include:

Obesity
Type 2 diabetes
Hyperinsulinemia
Hypothyroidism
Excessive growth hormone levels
Certain medications, such as steroids, androgens, and progestins
Testicular or adrenal cancer (in men)
Polycystic ovary syndrome (PCOS) (in women)
Cushing’s syndrome
A genetic disorder

Causes of high SHBG

High SHBG results could signal that the protein is attaching to too much testosterone, which decreases the amount of hormone that’s available for your tissues to use. This could lead to low testosterone symptoms.

Some of the possible causes of high SHBG include:

Liver disease
Hyperthyroidism
Eating disorders
Pregnancy
Growth hormone deficiency
Androgen deficiency
Ageing
Pituitary gland diseases
Hyperprolactinemia
Testicular disorders (in men)
Addison disease (in women)

SHBG isn’t part of routine lab testing, and it’s very likely that your doctor will order other tests along with it. A combination of tests allows your doctor to get a clearer picture of your hormone levels and determine the cause of any underlying conditions.

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