Quick Answer
What is SHBG? SHBG, or sex hormone-binding globulin, is a protein made mainly by the liver that carries testosterone and estrogen in the blood. Hormones bound tightly to SHBG are less available to tissues. Checking SHBG helps explain hormone results, especially when total testosterone looks normal but symptoms suggest otherwise, or the reverse.
Who this is for: women and men whose lab report includes SHBG, or who want to understand why it was ordered alongside hormone tests.
What SHBG Does
Sex hormones such as testosterone and estradiol travel through the blood attached to proteins. SHBG binds them tightly, while albumin binds them loosely. Only the small unbound portion, called free hormone, and the loosely bound portion are readily available to the body’s tissues.
Because of this, the amount of SHBG in your blood affects how much hormone is actually available. Two people with the same total testosterone can have different amounts of usable testosterone if their SHBG levels differ.[1]
SHBG binds sex hormones in the blood and affects how much is available to the body.
Why SHBG Is Tested
SHBG is most often checked:
- When total testosterone is borderline, to help estimate free testosterone
- When symptoms do not match total testosterone results
- In women, as part of evaluating symptoms such as irregular periods, acne or excess hair growth
- When a condition or medication that affects SHBG is present
SHBG is used together with total testosterone and albumin to calculate free testosterone when a direct measurement is not used.[1]
What Raises or Lowers SHBG
Factors that tend to raise SHBG
- Aging
- An overactive thyroid
- Liver disease
- Estrogen, including some forms of oral estrogen and birth control pills
- Some seizure medications
- Very low body weight
Factors that tend to lower SHBG
- Excess body weight
- Insulin resistance and type 2 diabetes
- An underactive thyroid
- Androgens and some steroid medications
- Polycystic ovary syndrome
Low SHBG is often seen with insulin resistance, which is one reason it can be a useful clue about metabolic health.
Making Sense of Your Results
SHBG is not usually interpreted on its own. A high SHBG with normal total testosterone may mean less testosterone is available to the body. A low SHBG may make total testosterone look low even when free testosterone is adequate. Reference ranges vary by lab, age and sex, so results are best reviewed with your provider alongside your symptoms and other tests.
How We Use SHBG at Lake Forest Regenesis
Allana orders SHBG when it adds useful information, such as when testosterone results are borderline or do not match your symptoms. She reviews it together with total and free testosterone, thyroid function, blood sugar and your health history, since many of those factors affect SHBG. Treatment decisions are based on the full picture, not on SHBG alone.
When to See a Provider
Talk with a provider if you have symptoms such as low libido, fatigue, irregular periods, acne or unusual hair growth. Ask about your results if your SHBG is flagged high or low, especially if you also have weight changes, thyroid symptoms or blood sugar concerns.
Have an SHBG result flagged on your labs? Allana can review it with your hormones, thyroid and blood sugar to see the full picture.
Frequently Asked Questions
Is high SHBG bad?
Not by itself. High SHBG may mean less hormone is available to tissues, which can matter if you have symptoms. It can also point to causes such as thyroid or liver changes.
Is low SHBG bad?
Low SHBG is often linked with excess weight and insulin resistance. It can be a helpful signal to look at metabolic health.
Can I change my SHBG level?
Sometimes. Treating thyroid problems, improving insulin resistance and losing excess weight can shift SHBG over time.
Do women need SHBG testing?
Sometimes. It is useful when evaluating symptoms such as irregular periods, acne or excess hair growth, and when interpreting testosterone levels in women.
References
- Bhasin S, et al. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2018;103(5):1715-1744. Read the guideline
- MedlinePlus. Testosterone levels test. U.S. National Library of Medicine. Read the article
This article is for general education and is not a substitute for individual medical advice. See our medical disclaimer.
