The Difference Between Total Testosterone and Free Testosterone

Total Testosterone vs. Free Testosterone: What You Need to Know

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Understanding testosterone levels can be confusing. Here’s a guide to the differences between total and free testosterone

While we tend to think of testosterone in relation to sexual function and muscular development, this hormone actually affects the entire body – in both men and women.

Testosterone is produced in the testes, ovaries, adrenal glands, and via precursor hormones; those that the body converts into testosterone.

As we age, testosterone levels decrease. However, aging itself isn’t always the culprit. Measuring testosterone levels can help diagnose a variety of maladies, including sexual dysfunction. These measurements assess total and/or free testosterone levels.

Free vs. Total Testosterone: What’s the difference?

98% of the testosterone the body produces is bound to either sex-hormone binding globulin (SHBG), or albumin. This is referred to as “bound testosterone.” The 2% that’s left is known as “free testosterone.”

This free classification of the hormone accounts for the amount that connects with testosterone receptors within the body’s cells. When a cell absorbs free testosterone, it enables its functionality, such as cell replication in the bones and muscles.

As you may have deduced, total testosterone calculates 100% of the hormone available in the bloodstream. While some testosterone tests only account for total testosterone, they might not be as helpful as once thought.

A 98% proportion is normal for bound testosterone – but obviously, anomalies can occur. Limiting tests to total testosterone levels overlooks the possibility of excessive bondage to either SHBG or albumin. If too little of the hormone is “free” to do its work, this can lead to issues, including poor muscle development, irritability, and lower sex drive.

Therefore, while total testosterone levels may appear healthy, low levels of free testosterone could lead to improper diagnosis and treatment plans.

Bioavailable Testosterone

Until recently, free testosterone was the only type considered biologically active. It turns out, however, that the portion of the hormone bound to serum albumin tends to become available in the capillary bed. Therefore, non-SHBG-bound testosterone is also deemed as “bioavailable.”

In a manner of speaking, bioavailable testosterone is like a reserve supply, ready for use when the body is low on free testosterone. However, scientists still don’t know how much bioavailable testosterone goes on to be absorbed by cells in these conditions.

In most cases, bioavailable and free testosterone run even. Exceptions to this are known to manifest due to certain medical conditions and medications. For example, corticosteroids and sex steroids may cause an increase or decrease in SHBG amounts. In such instances, medical professionals may have difficulty properly diagnosing abnormalities.

Other conditions that may cause diagnostic problems include:

  • Genetically caused SHBG-binding abnormalities
  • Liver disease
  • Severe systemic illness
  • Polycystic ovarian syndrome

Increasing Free Testosterone Levels

There are two ways to improve free testosterone levels. In general, anything that increases total testosterone levels (such as forms of exercise or supplementation) will also elevate free testosterone. The other method involves reducing SHBG bound testosterone.

While the aging process naturally increases SHBG bondage, other factors can accelerate the process. Levels of certain hormones such as insulin, growth hormone, estrogen, and thyroid hormones are known to affect SHBG bonding. Vitamins and herbs, including vitamin D and boron are thought to lower SHBG.

Hormonal Imbalances and Erectile Dysfunction

Obviously, testosterone plays a key role in the body’s sexual function. Imbalances in testosterone levels can cause erectile dysfunction (ED) and decreased libido. However, testosterone may be only one of a myriad of factors contributing to ED.

To find out more about possible causes of ED, as well as a solution, we encourage you to read Common and Not-So-Common Causes of Erectile Dysfunction.