Most people have never heard of SHBG, yet it quietly determines how much of your testosterone and estrogen your body can actually use. If you’ve had normal total testosterone but still feel off, SHBG is often the missing piece.
What SHBG Actually Does
SHBG, or Sex Hormone-Binding Globulin, is a protein made mainly in your liver that binds to testosterone and estrogen in your bloodstream. Once bound, that hormone becomes inactive — it’s still present in your blood, but it’s not available for your cells to use. Only the unbound, “free” portion is biologically active.
Why SHBG Levels Change
SHBG isn’t fixed — it rises and falls based on several factors:
- Age — SHBG tends to increase gradually as men get older, which is part of why free testosterone often declines even when total testosterone looks stable
- Thyroid function — an overactive thyroid raises SHBG, an underactive one lowers it
- Liver health — since SHBG is produced in the liver, liver conditions directly affect levels
- Body composition — higher body fat is generally associated with lower SHBG
- Medications — certain medications, including some used for prostate conditions, can raise or lower SHBG
Why This Matters for How You Feel
Two men can have identical total testosterone and feel completely different, simply because one has much higher SHBG binding up more of it. This is one of the clearest explanations for “normal labs, real symptoms” — the total number looked fine, but less of it was actually available to use.
Per the Endocrine Society, SHBG is considered an important piece of a complete hormone evaluation specifically because it explains discrepancies between total and free hormone levels.
Should You Get SHBG Tested?
If you’re investigating symptoms of low testosterone and your total testosterone came back normal, SHBG (alongside free testosterone) is one of the most useful next tests to help explain what’s actually happening.
You can order a Comprehensive Male Hormone Profile, which includes SHBG alongside testosterone markers, directly through Personalabs — no doctor’s visit required.
Frequently Asked Questions
Do I need to fast before an SHBG test?
No fasting is required for SHBG testing.
Is high SHBG bad?
Not inherently — it depends on context. High SHBG combined with low free testosterone and real symptoms is worth discussing with your doctor, while high SHBG with no symptoms may not need intervention.
Can SHBG explain low estrogen too?
Yes — SHBG binds estrogen as well as testosterone, so elevated SHBG can reduce available estrogen, which is relevant for both men and women.
Does weight loss affect SHBG?
Yes, significant weight loss is generally associated with rising SHBG levels, which is one reason hormone levels can shift during major body composition changes.
What’s a normal SHBG range?
Reference ranges vary by lab and by age, generally falling between roughly 10-57 nmol/L in adult men — your lab’s specific range should be used to interpret your result.
This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always talk to your doctor about your specific health situation.