What is an SHBG blood test?

This test measures the levels of SHBG in a sample of your blood. SHBG stands for sex hormone binding globulin. It's a protein made mostly in your liver. It binds (attaches) to sex hormones in your blood.

SHBG helps control the amount of sex hormones that are actively working in your body. When the SHBG protein binds to sex hormones, your tissues can't use those hormones. Your tissues can only use sex hormones that are "free," which means they aren't attached to proteins, such as SHBG.

An SHBG test is usually done if you have signs and/or symptoms of having too much or too little of the sex hormone testosterone. Testosterone is known as a "male" sex hormone, but females have testosterone in smaller amounts.

In adult males, testosterone controls sex drive, maintains muscle mass, and helps make sperm. In adult females, testosterone is important for healthy organs and the growth of bones and muscles. Measuring SHBG levels can provide information about how much of your testosterone is active in the tissues of your body.

Other names: testosterone-estrogen binding globulin, TeBG

What is it used for?

SHBG testing is most often used to gather information about how testosterone is working in the body for:

• Adult males who have symptoms that may be caused by too little testosterone
• Adult females who have symptoms that may be caused by too much testosterone

Usually, your health care provider will order a total testosterone blood test first. This test provides one measurement of all the testosterone in your blood sample, which includes free testosterone plus testosterone that's attached to proteins. But this test doesn't show how much of your testosterone is free for your body to use. So, you could have symptoms from too little or too much free testosterone even when your total testosterone level is normal.

If your total testosterone level doesn't explain your symptoms, your provider may order an SHBG blood test to help learn how much free testosterone you have. SHBG and total testosterone tests may also be done at the same time.

Why do I need an SHBG blood test?

You may need this test if you have signs and/or symptoms of abnormal testosterone levels, especially if results from a total testosterone test didn't explain your symptoms.

If you're male, you may need this test if you have symptoms of low testosterone levels, including:

• Low sex drive
• Difficulty getting an erection
• Fertility problems

If you're female, you may need this test if you have symptoms of high testosterone, including:

• Too much hair growth on the face and body
• Deepening of voice
• Having menstrual periods that aren't regular or no periods at all
• Acne
• Weight gain
• Fertility problems

What happens during an SHBG blood test?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Will I need to do anything to prepare for the test?

You don't need any special preparations for an SHBG test.

Are there any risks to the test?

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

What do the results mean?

Your provider will usually look at your SHBG blood test results along with the results of a total testosterone test. This helps your provider estimate how much free testosterone is in your blood.

If your SHBG levels are too low, it means that more of your total testosterone is likely to be available for your body to use.

Low levels of SHBG may be related to:

• Hypothyroidism
• Type 2 diabetes
• Obesity or being very overweight
• Overuse of steroid medicines and/or anabolic steroids
• Cushing's syndrome
• In females, polycystic ovary syndrome (PCOS).

It's also normal for SHBG levels to decrease with older age as the production of sex hormones also decreases.

If your SHBG levels are too high, it likely means that less of your total testosterone is free testosterone that's available for your tissues to use. So, your tissues may not be getting enough testosterone.

High levels of SHBG may be related to:

• Liver disease
• Hyperthyroidism
• Eating disorders
• In females, using estrogen in medicine, such as:
  • Hormone replacement therapy
  • Birth control pills
• In males, reduced production of sex hormones

Your provider may order other tests to check if your hormones are in balance with each other. If you have questions about your results, talk with your provider.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I need to know about an SHBG blood test?

An SHBG test may be used with other tests to help diagnose early puberty in children. Normally, SHBG levels are high in all children. The high levels prevent sex hormones from affecting body tissues. If SHBG levels are low, children may start puberty too early.