What is Sex Hormone Binding Globulin (SHBG) & why is it important for athletes?

What Is SHBG?

Sex Hormone Binding Globulin (SHBG) is a protein made by the liver that binds to sex hormones, primarily testosterone and oestrogen, in the bloodstream. It controls how much of these hormones are “free” and biologically active.

For athletes, SHBG plays a role in hormone availability. Even if your total testosterone or oestrogen levels are normal, high SHBG can reduce the amount of free hormone available to support muscle growth, energy, recovery, and libido.

"SHBG regulates the availability of key hormones like testosterone and oestrogen by binding to them in the bloodstream. For athletes, high or low SHBG levels can impact muscle development, recovery, and hormonal balance. I recommend testing SHBG alongside total and free testosterone to understand how much hormone is actually available to your body. It's especially useful if you're experiencing symptoms of low energy, poor recovery, or hormonal disruption despite normal testosterone levels."

Dr Thom Phillips

How SHBG Affects Performance

1. Hormone Availability

   SHBG binds tightly to testosterone. The higher your SHBG, the less free testosterone is available to support strength, recovery, and lean muscle mass.

2. Training Adaptation & Recovery

   Low free testosterone, due to high SHBG, can lead to slower muscle repair, reduced gains, and persistent fatigue.

3. Energy & Mood

   Reduced availability of active hormones may also impact energy, focus, and motivation — key mental aspects of athletic performance.

What are normal SHBG levels for athletes?

We looked at blood test data from EDGE customers and found the median sex hormone binding globulin levels for women are 61.2 nmol/L and 31.3 nmol/L for men.

Here is a breakdown of SHBG levels by age:

Source: EDGE customer blood test results Apr 2023 – March 2025.

The labs we used to analyse blood samples state a healthy range for SHBG is generally between 24.6 – 122 nmol/L for women and 16.5 – 55.9 nmol/L for men.

What Affects SHBG Levels?

• Under-fuelling or low energy availability

• Endurance training or high training volume

• Use of oral contraceptives (in women)

• Thyroid hormone imbalances (especially hyperthyroidism)

• Ageing (natural SHBG increases over time)

• Liver health and some medications

Symptoms of High SHBG / Low Free Hormone Availability

• Reduced strength or difficulty building muscle

• Low libido or changes in menstrual cycle

• Fatigue or slower recovery

• Mood changes or low motivation

• Normal total testosterone but symptoms of deficiency

Why Test SHBG?

• To evaluate unexplained symptoms when total testosterone appears normal

• To assess hormonal bioavailability in men and women

• As part of a RED-S or hormonal imbalance investigation

• To interpret total vs free testosterone or oestradiol more accurately

• When using oral contraceptives or recovering from overtraining

How to Optimise SHBG Levels

• Ensure you are fuelling adequately for your training load

• Address thyroid imbalances if present

• Consider zinc, vitamin D, and healthy fat intake — all of which support hormone balance

• Reduce training volume temporarily if SHBG is chronically high

• Seek professional guidance if using hormonal contraception and experiencing symptoms

In Summary

• SHBG controls how much testosterone or oestrogen is freely available in your body

• High SHBG = less free hormone = reduced strength, libido, and recovery

• Best tested alongside total and free testosterone or oestradiol for full clarity

• Important marker in RED-S, hormonal imbalance, and performance plateaus