Laboratory test · Hormones and thyroid
SHBG
- Sample: venous blood
- Preparation: morning fasting; men 7–10 h
Test price
- Sample
- venous blood
- Preparation
- morning fasting; men 7–10 h
Paymentcash, cards and instalments
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SHBG (sex hormone-binding globulin) is a liver-produced protein that binds testosterone and oestradiol in blood. Testing measures SHBG to assess how much testosterone is actually available to tissues. It is performed in men with suspected testosterone deficiency and women with signs of excess male hormones, for example in polycystic ovary syndrome (PCOS).
Who is this test for
- men with reduced libido, erectile dysfunction, fatigue or muscle loss, particularly when total testosterone is borderline;
- older men and those with obesity, diabetes, liver or thyroid disease, because these conditions alter SHBG;
- women with excessive hair growth, acne or irregular cycles;
- women with suspected polycystic ovary syndrome (PCOS).
What SHBG is and what it shows
SHBG binds testosterone tightly and albumin weakly, leaving only around 2 % of testosterone free in blood. Tissues cannot use testosterone bound to SHBG, but can use free and albumin-bound testosterone. The more SHBG present, the less testosterone is available to tissues, and vice versa.
Tests total testosterone measures all testosterone together. When SHBG is altered, total testosterone may be misleading. SHBG is therefore rarely interpreted alone, but alongside total and free testosterone, and in women often with the free androgen index (FAI).
SHBG levels are affected by other hormones and metabolism. Insulin and male hormones reduce its production in the liver, while thyroid hormones and oestrogens increase it. Low SHBG therefore commonly accompanies insulin resistance and excess weight, but is not a diagnostic test for them.
Save with a panel
Test SHBG is also included in these panels.
Preparation and sample
SHBG is measured in venous blood and varies little during the day. Since it is almost always measured alongside testosterone, follow testosterone preparation: attend in the morning after fasting for 8 to 12 hours (water is allowed), and not during acute illness. Men should have blood drawn between 7 and 10 o’clock. In women the cycle day is not crucial unless the doctor instructs otherwise.
Mention hormonal contraception, hormone replacement therapy, thyroid medicines, testosterone or anabolic steroids, corticosteroids or epilepsy medicines, because these alter SHBG. Do not stop medicines yourself. If you take biotin (for example, hair and nail supplements), mention this when your blood is drawn.
How results are interpreted
The reference interval depends on sex, age and method and is printed on your report. SHBG is generally higher in women than men. Your doctor interprets results with total and free testosterone, symptoms, age and medicines.
Elevated SHBG
In men, SHBG gradually increases with age. It is also raised by an overactive thyroid, liver disease, oestrogen-containing medicines such as combined contraceptive pills and oral replacement therapy, pregnancy, certain epilepsy medicines, very low body weight and eating disorders. Men with high SHBG may have normal total but low free testosterone, so deficiency symptoms may occur despite a normal total result.
Low SHBG
The most common causes are obesity, insulin resistance, type 2 diabetes and PCOS. It is also lowered by an underactive thyroid, taking testosterone, anabolic steroids or corticosteroids, and less commonly adrenal diseases. In women, low SHBG means more testosterone is free, so signs of excess male hormones may occur despite normal total testosterone. Because low SHBG often accompanies insulin resistance, the doctor may also request glucose or insulin.
Free androgen index (FAI)
FAI is the ratio of total testosterone to SHBG, interpreted by a doctor. It is used mainly in women, for example when assessing PCOS. It is unreliable in men, particularly when SHBG is low, so free testosterone is assessed instead.
How to arrange testing
You can come for blood collection without an appointment or referral at one of our branches throughout Croatia (listed on the Contact). Attend in the morning after fasting; men should attend between 7 and 10 o’clock. Prices for all tests and panels are in the service price list. SHBG is measured with total testosterone and albumin in the Free testosterone panel, and in women with suspected polycystic ovary syndrome as part of the PCOS panel.
Frequently asked questions
What does low SHBG mean in women?
Low SHBG means a larger proportion of testosterone is free and active, which may worsen acne, hair growth and irregular cycles. It most often accompanies PCOS, excess weight and insulin resistance; the doctor assesses its cause and meaning alongside other results.
What does high SHBG mean in men?
High SHBG binds more testosterone, leaving less available to tissues. This is more common in older age and with liver disease or an overactive thyroid. The doctor then assesses free testosterone, rather than total alone.
Does contraception affect SHBG?
Combined contraceptive pills containing oestrogen raise SHBG, lowering free testosterone. Results in women taking contraception are therefore interpreted differently, and international PCOS guidelines advise measuring male hormones at least three months after stopping hormonal contraception when necessary, using another form of pregnancy protection. The gynaecologist makes this decision.
Should SHBG be measured without testosterone?
Rarely. SHBG is most useful alongside total testosterone, because only together do they show how much testosterone is available to tissues. It is therefore usually measured as a panel.