Testosterone Replacement Therapy (TRT)

Peter Attia: Testosterone replacement therapy TRT has been a growing topic of interest as an intervention not just for people with specific hormonal disruptions but simply as a health promoting measure for men in their later years. Joe Rogan and the manosphere of health influencers have put TRT in the forefront of many men's minds including myself. What I'd like to understand is how much reduced free testosterone would warrant TRT and the potential risks and benefits if used correctly.

Total testosterone can be understood in three broad categories:

• Free testosterone (1-4%): bio-available to the body to be used

• Albumin bound testosterone: loosely bound, held as a reservoir

• Sex Hormone Binding Globulin (SHBG) bound testosterone: tightly bound for hormone regulation

These three types in sum are your total testosterone and what is most often measured in clinics. However, free testosterone is the only measure that is generally considered valuable for deciding on TRT. Most labs will use a calculated free testosterone (cFT) rather than measure free testosterone due to the complexities of direct measurement. That being said, many guidelines still use total testosterone to determine cutoffs despite free testosterone being a more accurate measure.

As an example, normal amounts of testosterone are shown in this study:

Our final analytic cohort contained 1,486 men. Age-specific middle tertile levels were 409-558 ng/dL (20-24 years old), 413-575 ng/dL (25-29 years old), 359-498 ng/dL (30-34 years old), 352-478 ng/dL (35-39 years old), and 350-473 ng/dL (40-44 years old). Age-specific cutoffs for low testosterone levels were 409, 413, 359, 352, and 350 ng/dL, respectively.

When making the decision on whether TRT is right for you, its best to consider these factors and the impact some lifestyle changes like exercise can make not just on your total testosterone, but also how it may liberate additional free testosterone from your other bounded reservoirs.

This 2017 study reviewed the impact of various exercise types on elderly men's testosterone levels:

TT was significantly increased following HIIT (~17%; P < 0.001) with most increase occurring during preconditioning (~10%; P = 0.007). Free-T was unaffected by conditioning exercise (P = 0.102) but was significantly higher following HIIT compared to baseline (~4.5%; P = 0.023). Cortisol remained unchanged from A to C (P = 0.138). The present data indicate a combination of preconditioning, and HIIT increases TT and SHBG in sedentary older males, with the HIIT stimulus accounting for a small but statistically significant increase in free-T.