SHBG (sex hormone-binding globulin)

SHBG, sex hormone-binding globulin, is a transport protein made mainly in the liver. It binds the sex hormones dihydrotestosterone, testosterone and – somewhat more weakly – oestradiol and carries them through the blood. SHBG is measured in serum. The value is mainly considered together with testosterone, because only both together show how much hormone is actually freely available. In the test catalogue, SHBG is listed as a single parameter under the topic of acne, because the amount of free male hormones influences the sebaceous glands of the skin.

What SHBG does in the body

Only the small share of sex hormones that is not tightly bound to SHBG can enter the cells and act there. SHBG thus regulates how strongly testosterone and oestradiol reach the skin, hair roots, muscles, bones and brain. At the same time it serves as a reserve from which hormones are released gradually, and it slows their breakdown. The liver adapts SHBG production to metabolism: oestrogens and thyroid hormones increase it, while insulin, male hormones and growth hormone reduce it. SHBG therefore reflects not only the hormone balance but also sugar metabolism and liver function.

Low SHBG – what happens in the body?

When little SHBG is present, a larger share of the hormones is free. In women this strengthens the effect of male hormones: the sebaceous glands produce more sebum, and acne, oily skin, increased hair growth on face and body and irregular cycles become more likely. A high insulin level is often behind it, because insulin slows SHBG production in the liver – typical of insulin resistance, overweight, fatty liver and polycystic ovary syndrome (PCOS). Studies have linked low SHBG levels with type 2 diabetes. An underactive thyroid and the intake of male hormones also lower the value. In men, total testosterone then often appears low, although the free share may be sufficient.

High SHBG – what happens in the body?

With a lot of SHBG, a larger share of the hormones is bound and not available to the tissues. In men this can lead to signs of a lack of free testosterone, such as declining libido, lower muscle strength and lack of drive, even though total testosterone is normal or even raised. High levels arise with plenty of oestrogen, for example in pregnancy or with hormonal contraception, with an overactive thyroid, with liver disease, with very low body weight and with certain medicines for seizures. In men, SHBG also rises slowly with age. A high value is therefore always considered together with testosterone, oestradiol and the thyroid values.

The interpretation is given in your report.