What Is SHBG? Why This One Protein Can Change How Your Testosterone Labs Look

You can have a testosterone level that looks perfectly reasonable on paper and still have symptoms.

You can also have a total testosterone level that looks higher than expected without necessarily having a large amount of testosterone available for your body to use.

One reason for that disconnect is SHBG — sex hormone-binding globulin.

SHBG does not get nearly as much attention as testosterone, estrogen or progesterone, but it can make a meaningful difference in how hormone labs are interpreted.

At AdoreU, this is one of the reasons I don’t look at a single testosterone number in isolation.

What Is SHBG?

SHBG stands for sex hormone-binding globulin.

It is a protein that binds to sex hormones in the bloodstream, particularly testosterone and estradiol.

Think of SHBG almost like a carrier.

Most testosterone circulating in the bloodstream is attached to proteins. Only a small amount circulates freely.

When testosterone is tightly bound to SHBG, it is not as readily available to tissues.

That means your total testosterone level doesn’t necessarily tell us how much testosterone is available for your body to use.

Total Testosterone and Free Testosterone Are Not the Same Thing

When you see total testosterone on a laboratory report, that number includes testosterone that is both bound and unbound.

Free testosterone represents the much smaller portion that is not bound to proteins.

This distinction matters.

Two people can have similar total testosterone levels while having very different amounts of free or bioavailable testosterone.

Why?

One reason can be SHBG.

If one person has higher SHBG, more testosterone may be tightly bound.

If another person has lower SHBG, a larger percentage may remain available.

That is why I may look at total testosterone, free testosterone and SHBG together rather than deciding whether someone’s hormone status is “good” or “bad” based on total testosterone alone.

What Can Affect SHBG?

SHBG is not the same in every person, and it can change.

Several factors may influence it, including:

• estrogen exposure

• thyroid function

• liver health

• metabolic health

• body composition

• certain medications

• age

• individual physiology

This is another reason hormone evaluation needs to be individualized.

The same total testosterone value may mean something very different depending on what the rest of the laboratory picture looks like.

What Does a Higher SHBG Mean?

When SHBG is higher, a greater amount of testosterone may be bound.

That can sometimes result in a person having a total testosterone level that appears adequate while the amount of free testosterone is lower.

But this is important:

High SHBG by itself does not diagnose a hormone problem.

It is one piece of information.

If someone is experiencing fatigue, low libido, decreased motivation, changes in body composition or other symptoms, I still want to know what else is happening.

What does the free testosterone show?

What are the other hormone levels?

What medications are they taking?

How are they sleeping?

What does their thyroid look like?

What is happening metabolically?

There is rarely one number that explains everything.

What Does a Lower SHBG Mean?

Lower SHBG means less testosterone is tightly bound to that protein.

Depending on the total testosterone level, that can result in a greater proportion of testosterone being free or bioavailable.

Again, that does not automatically mean someone has “too much testosterone.”

It means we need context.

The total testosterone, free testosterone, SHBG, symptoms, treatment history and other laboratory findings all matter.

Hormone interpretation gets shaky very quickly when one number is pulled out of the report and treated as though it explains everything.

Why Two People With the Same Testosterone Level Can Feel Completely Different

This is one of the biggest concepts I want patients to understand.

Imagine two people who both have the exact same total testosterone level.

On paper, their testosterone looks identical.

But one has higher SHBG and the other has lower SHBG.

The amount of testosterone available to tissues may therefore be different.

And SHBG is still only one variable.

People also differ in:

• hormone metabolism

• body composition

• medications

• health conditions

• hormone receptor sensitivity

• age

• genetics

• lifestyle

• stress

• sleep

• metabolic health

This helps explain why there is not one magical testosterone number that guarantees every person will feel the same.

Your laboratory values matter. But so does how your individual body responds.

SHBG Is Helpful — but It Isn’t a Magic Number Either

It would be easy to swing too far in the opposite direction and make SHBG the new number everyone becomes obsessed with.

I don’t think that is helpful either.

SHBG is a tool.

Total testosterone is a tool.

Free testosterone is a tool.

Estradiol, progesterone, thyroid markers and other laboratory values are tools.

The purpose of testing is not to hunt through a laboratory report until we find one number to blame everything on.

The purpose is to put the pieces together.

Symptoms Still Need Context

Fatigue, brain fog, poor sleep, low libido, mood changes, changes in weight or difficulty building muscle can occur for many reasons.

Hormones may be contributing.

But depending on the individual, we may also need to consider:

• sleep quality

• chronic stress

• thyroid function

• insulin resistance and metabolic health

• nutrition

• nutrient deficiencies

• exercise and muscle mass

• medications

• inflammation

• autoimmune conditions

• gut health

• other medical conditions

This is why I don’t make promises that changing one hormone level is going to fix every symptom.

Sometimes hormone optimization is an important part of the answer.

Sometimes there are multiple layers contributing to how someone feels.

And sometimes we need to address those layers together.

What I Look at During a Hormone Evaluation

When testosterone is part of the evaluation, I may consider total testosterone, free testosterone and SHBG together rather than relying on one value alone.

But I also want to know about you.

When did your symptoms start?

How are you sleeping?

Has your libido changed?

How is your energy?

What has happened to your mood or motivation?

Have you noticed changes in strength or body composition?

Are you taking medications or hormones that could influence your results?

What do your other laboratory markers show?

And if you are already receiving treatment, how have both your symptoms and labs changed over time?

The goal is not to make your laboratory report fit a predetermined protocol.

The goal is to understand what the laboratory report means in the context of you.

Why Follow-Up Matters

Hormone optimization is not something I want to manage based on one blood draw forever.

If treatment is appropriate, follow-up gives us more information about how your body actually responds.

That may include repeat laboratory testing along with a review of:

• symptoms

• treatment response

• side effects

• sleep

• energy

• mood

• libido

• body composition

• overall goals

Sometimes the numbers change and the patient feels better.

Sometimes the numbers change and the patient does not feel significantly better.

When that happens, simply pushing the hormone level higher may not be the answer.

We may need to look more closely at other factors contributing to the symptoms.

That is why hormone care can sometimes require a layered approach rather than a one-number solution.

The Bottom Line

SHBG can influence how testosterone circulates in your bloodstream and how much may be available to tissues.

That is one reason two people with similar total testosterone levels can have very different hormone profiles — and potentially very different experiences.

But SHBG is not a diagnosis by itself.

It is one part of a much larger picture.

At AdoreU, hormone evaluation is built around that larger picture: your symptoms, laboratory findings, health history, goals and how your body responds over time.

Because good hormone care should never come down to one number.

Wondering What Your Hormone Labs Actually Mean?

If you have hormone results but still don’t understand why you feel the way you do, a comprehensive evaluation may help put the pieces together.

AdoreU provides individualized hormone evaluation and hormone optimization for women and men in O’Fallon, Missouri and throughout the St. Charles County area.

REQUEST A COMPREHENSIVE ASSESSMENT

References

Maclaran K, Panay N. The Safety of Postmenopausal Testosterone Therapy. Women’s Health. 2012;8(3):263–275.

Morgentaler A, et al. Fundamental Concepts Regarding Testosterone Deficiency and Treatment: International Expert Consensus Resolutions. Mayo Clinic Proceedings. 2016.

Carruthers M, Trinick TR, Wheeler MJ. The Validity of Androgen Assays. The Aging Male. 2007;10:165–172.