SHBG (sex hormone binding globulin)

Women: 32 to 128 nmol/L · Men: 18 to 54 nmol/L

Women run higher than men (roughly 32 to 128 versus 18 to 54 nmol/L), it rises with age in men, and it is higher on the combined pill, on HRT and in pregnancy.

SHBG is a protein made by the liver that carries testosterone and oestradiol around the blood. Hormone that is bound to SHBG is not active, so the amount of SHBG changes how much of the total testosterone is actually available to the body. It is measured mainly to make sense of a testosterone result.

It is requested alongside testosterone in men with symptoms of low testosterone and in women with excess hair growth or polycystic ovary syndrome, so that free testosterone or the free androgen index can be worked out. It also gives a clue to how the liver, thyroid and insulin are behaving.

• The combined contraceptive pill, HRT and pregnancy, through oestrogen
• An overactive thyroid
• Liver disease and heavy alcohol use
• Older age in men, in the general population
• Low body weight and eating disorders
• Some anti-epileptic medicines
• Lower body fat and higher levels of physical fitness

• Heavier body weight, insulin resistance and type 2 diabetes
• Polycystic ovary syndrome
• An underactive thyroid
• Testosterone, anabolic steroids and some progestogens
• Steroid medicines and growth hormone excess
• Nephrotic syndrome (protein loss through the kidneys)

• The combined pill can double it without anything being wrong
• Very fit or lean people run higher, heavier people lower
• It shifts with the thyroid, so a change often reflects thyroid hormone rather than the sex hormones

No fasting needed, but it is usually drawn with the same morning sample as testosterone so the two can be read together.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.