Sex Hormone Binding Globulin

Other names: SHBG

SHBG (sex hormone binding globulin) is a protein, which is produced by the liver. SHBG binds to hormones, including testosterone, oestradiol and dihydrotestosterone (DHT) and carries them around the blood in an inactive state. The amount of SHBG in the blood is affected by different health conditions, as well as age and gender; irregular levels of SHBG may affect the amount of testosterone available for use in the body.

Why is the test used?

The test is used to determine the amount of testosterone in the blood; in men, it is primarily used to test for deficiency of testosterone and in women it is used to test for overproduction of testosterone. The SHBG test is usually carried out alongside the total testosterone test.

In males, the test is usually ordered when a patient has erectile dysfunction, decreased libido and infertility.

In females, the test is usually ordered when a patient has acne, infertility, amenorrhoea (when the periods stop or become infrequent) or excessive hair growth.

The total testosterone test usually provides sufficient information for doctors to reach a diagnosis; however, the SHBG test may be carried out if the test results don’t match the clinical signs and symptoms.

How is the test done?

The test is performed by taking a sample of blood from a vein in the arm; a needle is inserted into the vein and the blood is collected in a syringe. When the doctor has a sufficient amount of blood, it will be bottled, labelled and sent to the laboratory for testing.

What do the test results show?

If levels of SHBG are much higher than usual, this usually indicates that there is less free testosterone available for use in the tissues; this often causes a decrease in libido.

If levels of SHBG are lower than normal, this means there is a larger quantity of free testosterone available for use; in females, this can contribute to excessive hair growth.

Increased SHBG levels are usually seen in patients with health conditions, including liver disease, anorexia and hyperthyroidism. Drugs such as oral contraceptives and hormone replacement therapy may also cause levels to increase.

Decreased levels of SHBG may be seen in patients with Cushing’s disease, obesity and hypothyroidism.

Specific Blood Tests

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