SHBG Explained: The Protein That Holds Testosterone
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[Glossary · How doses act in the body]

SHBG (sex hormone-binding globulin)

Also called SHBG, sex hormone binding globulin, TeBG, testosterone-estrogen binding globulin · Reviewed

Definition: SHBG (sex hormone-binding globulin) is a protein made mostly in the liver. It grabs onto sex hormones such as testosterone and estrogen. Hormone bound to SHBG cannot act on tissues, so SHBG helps decide how much of your testosterone is actually usable. An SHBG test measures how much of this protein is in your blood.

Why it matters for testosterone results

A total testosterone test counts bound and unbound hormone together. MedlinePlus says this means you can have symptoms of too little or too much free testosterone even when total testosterone looks normal. SHBG and total testosterone are often read together to estimate the free part.

The 2018 Endocrine Society guideline says that in men whose total testosterone is near the lower limit of normal, or who have a condition that changes SHBG, free testosterone should be measured or estimated with an accurate formula.

Labels describe the binding differently. The Depo-Testosterone label says testosterone in plasma is 98% bound to this globulin and about 2% free. The Xyosted label says about 40% is bound to SHBG, 2% is free and the rest is loosely bound to albumin and other proteins.

What can move SHBG

  • Linked to lower SHBG (MedlinePlus): underactive thyroid, type 2 diabetes or insulin resistance, obesity, overuse of steroid medicines or anabolic steroids, and Cushing's syndrome.
  • Linked to higher SHBG (MedlinePlus): liver disease, overactive thyroid, some eating disorders, and estrogen-containing medicines.
  • Medicines matter. MedlinePlus says birth control pills, estrogen therapy and anabolic steroids can affect SHBG, so tell your provider everything you take.

Each lab sets its own reference range, so read your result against the range printed on your own report, and talk with your clinician about what it means for you.

Read more on Dose Track: Low testosterone · Logging lab results in Dose Track

General education drawn from labels and published studies, not personal medical advice. Your prescriber, pharmacist and the label that came with your product are the final word.
Free testosteroneFree testosterone is the part of testosterone in your blood that is not attached to a protein. Most… Estradiol (E2)Estradiol , or E2, is the main type of estrogen in women of childbearing age. Men make small amounts too.… Testosterone esterA testosterone ester is testosterone with a fatty acid chain attached, such as cypionate or enanthate. The… TSH (thyroid-stimulating hormone)TSH (thyroid-stimulating hormone) is made by the pituitary gland and tells the thyroid how much hormone to…

Frequently asked questions

Is high SHBG bad?+
Not on its own. MedlinePlus says high SHBG likely means less of your total testosterone is available to tissues. Your clinician reads it alongside total and free testosterone.
Do I need to fast for an SHBG test?+
MedlinePlus says no special preparation is needed, but you should tell your provider about medicines with hormones in them, since they can affect SHBG.

Sources

  1. MedlinePlus (NIH): SHBG Blood Test
  2. MedlinePlus (NIH): Testosterone Levels Test
  3. Bhasin S et al. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab 2018 (abstract). PMID 29562364
  4. Depo-Testosterone (testosterone cypionate) US prescribing information, DailyMed
  5. Xyosted (testosterone enanthate) US prescribing information, sections 1, 5 and 12.3, DailyMed

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