- SHBG is a protein mainly produced in the liver that binds to sex hormones. It mostly impacts the amount of testosterone your cells and tissue can use.
- An SHBG test offers your health care provider a better picture of your sex hormone levels than would just looking at your testosterone levels.
- If your SHBG level is high or low, talk to your doctor about the best course of action.
If you’ve ordered an at-home test from Hone, you probably saw that one of the biomarkers our physicians test for is sex hormone binding globulin (SHBG). But what is it, why do your levels matter, and what does it have to do with testosterone?
SHBG is a protein that’s mostly produced in your liver. As the name suggests, it binds to your sex hormones—including testosterone, dihydrotestosterone (DHT), and estradiol (estrogen)—and carries them throughout your bloodstream.
Think of SHBG as a regulator of how much of these sex hormones your body can use. Your cells can only access sex hormones that aren’t attached to SHBG. Here’s the gist on why your SHBG levels, which fluctuate throughout your life, can be a good gauge for whether your sex hormones are out of balance (1).
What Are Normal SHBG Levels for Men?
In adult men, normal SHBG levels should be between 13.3-89.5 nmol/L.
How Does SHBG Affect Testosterone Levels?
Although SHBG binds to both testosterone and estrogen, it has more of an affinity for male hormones, and therefore it mainly impacts the body’s availability of testosterone.
Your body has a small amount of what’s called free testosterone, meaning it’s not attached to any protein. It also has some testosterone that is attached to the protein albumin. Both albumin-bound and free testosterone are considered bioavailable, meaning your cells and tissue can easily use this testosterone.
However, most of the body’s testosterone—normally about 70 percent—is bound to SHBG. This testosterone is basically locked up; your cells and tissue can’t use it (1). Your body can only use free or albumin-bound testosterone. Although albumin-bound T has slightly different characteristics when it comes to bioavailability.
When SHBG is too high or too low, it affects your body’s access to testosterone. A high SHBG level means that less free testosterone is available to help regulate your mood, energy, sex drive, and more. A low SHBG level means that more T is available (2).
SHBG at a Glance
- SHBG binds to testosterone and transports it throughout your body. Your body can’t use testosterone that is bound to SHBG.
- If your SHBG levels are too high, there is less free testosterone available to help regulate your mood, sex drive, and more.
- Low SHBG levels indicate that there is more free testosterone for your body to use.
Why Would I Need an SHBG Test?
If you have symptoms of low or high testosterone, your doctor might analyze your free and total testosterone (the combo of free T and bound T). Hone’s assessment measures both of these.
But sometimes these testosterone levels don’t offer your healthcare provider a complete picture of what’s going on with your sex hormones or your body. Adding an SHBG test can help determine the ratio of testosterone that’s actually available to your cells and tissue. That’s because it further differentiates the fraction of SHBG-bound T, from albumin-bound-T, and free T. These ratios can be especially important if your total T appears within the normal range but you’re having symptoms related to low T. Plus, an out-of-range SHBG level can sometimes indicate a health concern (3).
What Does It Mean if My SHBG Is Low?
If your SHBG is on the low end of the spectrum, then it may mean too little of the protein is binding to testosterone, leaving too much T accessible to cells and tissue (4). While having more free testosterone sounds like a good thing, your body needs T in the right balance. Too much can cause health issues.
What Causes Low SHBG Levels?
Several underlying conditions are linked to low SHBG.
- Insulin resistance
If your body is less sensitive to the effects of insulin, it produces more as a result. Insulin resistance reduces SHBG production in the liver (5).
- Metabolic syndrome
- Non-alcoholic fatty liver disease (NAFLD) (6)
- Certain cancers
- Cushing’s syndrome
How to Increase SHBG levels
Some lifestyle changes can up your SHBG levels (7, 8, 9, 10 ):
- Weight Loss
- Eating a healthy diet
- Regularly drinking caffeine
- Prescription medications
Summary: Low SHBG Levels
- If your SHBG levels are low, your body may have too much free testosterone.
- Several health conditions are linked to low SHBG levels, including obesity, insulin resistance, and metabolic disease.
- Making healthy lifestyle changes can help increase your SHBG levels.
What Does High SHBG Mean?
If your SHBG levels are elevated, it may mean that too much of the protein is binding to testosterone, leaving too little T accessible to cells and tissue (4).
What Causes High SHBG?
Several conditions are linked to high SHBG
- Growth hormone (GH) deficiency (11, 12)
- Hyperthyroidism (13)
- Liver conditions or damage, including cirrhosis or hepatitis (14)
- Viral infections, including HIV (15)
- Prostate cancer is also linked to high SHBG (16)
How to Lower High SHBG levels
In some cases, adding more protein to your diet may lower SHBG levels, but more research is needed to conclude how diet can help. And certain medications, mainly prescription glucocorticoids when appropriately prescribed for certain conditions, may also be beneficial (16, 17).
Summary: High SHBG Levels
- If your SHBG levels are high, your body won’t have enough free testosterone available.
- Several health conditions are linked to high SHBG levels, including hyperthyroidism, prostate cancer, liver conditions, and GH deficiency.
- Medications and diet changes can help lower your SHBG levels.