SHBG levels: what sex hormone binding globulin tells you

What is SHBG?

SHBG (sex hormone binding globulin) is a protein made mostly in the liver. It binds sex hormones, especially testosterone and estrogen, and controls how much of them is free to act on your tissues. Hormone bound to SHBG cannot work on tissues; the free part can.

On its own, SHBG says little. Its value comes from reading it with total testosterone: together they let a lab estimate free testosterone. That is why MedlinePlus says an SHBG test is most often ordered when someone has symptoms of too much or too little testosterone that total testosterone alone does not explain, such as a man with low-testosterone symptoms and a normal total level, or a woman with signs of excess androgens.

SHBG normal range

Source: ARUP Laboratories. SHBG is reported in nmol/L at almost every lab, so no conversion is usually needed, but ranges differ between labs. Women run higher than men, and ARUP's range for men widens from age 50. SHBG is naturally very high in children, which keeps sex hormones from acting before puberty.

When doctors order SHBG

MedlinePlus lists the usual reasons:

• Men with symptoms of low testosterone, such as low sex drive, trouble getting an erection, fatigue, muscle loss or fertility problems
• Women with symptoms of high testosterone, such as extra facial or body hair, a deeper voice, irregular or absent periods, acne or fertility problems
• Helping diagnose and monitor PCOS, together with other results
• People on menopause hormone therapy or treatment for hormone disorders
• Children with signs of early puberty

Test SHBG with testosterone at homeSHBG is on five SiPhox panels, with total and calculated free testosterone, from $124 a test plus $25 shipping.

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Reading SHBG with testosterone

A calculated free testosterone turns these patterns into a number, which is why labs report SHBG, total and free testosterone together.

What high SHBG means

High SHBG ties up more testosterone, so less is free, and a man can have symptoms of low testosterone even with a normal total level. MedlinePlus links high SHBG to:

• Liver disease
• An overactive thyroid (hyperthyroidism); check TSH
• Some eating disorders
• Estrogen-containing medicines, such as birth control pills or menopause hormone therapy
• Low sex hormone production in men

What low SHBG means

Low SHBG leaves more testosterone free. MedlinePlus links it to:

• Obesity
• Type 2 diabetes or insulin resistance
• An underactive thyroid (hypothyroidism)
• Overuse of steroid medicines or anabolic steroids
• Cushing's syndrome
• Polycystic ovary syndrome (PCOS) in women

Because low SHBG is linked with insulin resistance and type 2 diabetes, a low result is a prompt to look at metabolic markers such as HbA1c and C-peptide. In women, low SHBG is also linked with PCOS.

Worked example: low SHBG with irregular periods

Say a 27-year-old woman with irregular periods and acne gets an SHBG of 18 nmol/L, below ARUP's 25 to 122 nmol/L range for her age, and a total testosterone of 52 ng/dL, just above MedlinePlus's 8.4 to 48.1 ng/dL range for women 17 to 50. With so little SHBG, a larger share of that testosterone is free, which fits her symptoms.

Obesity, insulin resistance, an underactive thyroid and PCOS are all on MedlinePlus's list for low SHBG, so the result is a reason to look further, not a diagnosis. MedlinePlus says SHBG helps diagnose PCOS only together with other results.

Questions for the doctor: Should we calculate free testosterone and check LH and FSH as part of a PCOS workup? Given the link with insulin resistance, should I have fasting insulin and HbA1c tested? Should we rule out an underactive thyroid with TSH?

What can change SHBG

• Body weight and insulin resistance. Obesity and insulin resistance are linked with low SHBG.
• Thyroid function. An overactive thyroid is linked with high SHBG and an underactive one with low SHBG, so thyroid disease is worth ruling out.
• Hormones and medicines. Birth control pills and estrogen therapy raise it; anabolic steroids and steroid medicines lower it. Do not change any prescribed medicine without your doctor.
• Liver health. Liver disease raises SHBG; see ALT.

How to test SHBG

• No special preparation is needed for SHBG itself (MedlinePlus).
• Test it at the same time as total testosterone, in the morning, so free testosterone can be calculated from a matched pair.
• Tell whoever orders the test about birth control, hormone therapy or anabolic steroids.

Common questions about SHBG

Does SHBG change with age?

The sources disagree on direction. MedlinePlus says it is normal for SHBG to decrease with older age as sex hormone production falls, while ARUP's range for men is higher from 50 (19 to 76 nmol/L, against 17 to 56 at 18 to 49). The practical rule: compare your result with the age band printed on your own report.

What is the free androgen index?

Total testosterone divided by SHBG, times 100. Hormone Focus reports it. The 1999 Vermeulen study found it is not a reliable index of available testosterone, so for men a calculated free testosterone is the better number. See our free androgen index page.

Which at-home tests include SHBG

SiPhox Health includes SHBG on five of its six panels:

Heart & Metabolic is the only panel without it. Hormone Focus is the natural choice if SHBG is the question, since it gives the full picture of total, free and % free testosterone. See the at-home testosterone test guide or our SiPhox review.

A note on home samples: SiPhox's partner lab tests capillary blood collected from the upper arm. SiPhox says its results show a 95% to 99% correlation with venous draws in its own quarterly comparisons against Labcorp and Quest, but it has not published a study of the EasyDraw device. If a result would change a treatment decision, confirm it with a venous test through your doctor.

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