Free Testosterone
Concept
Refers to the unbound, biologically active form of testosterone, which is difficult to measure directly and is often estimated.
Mentioned in 2 videos
Videos Mentioning Free Testosterone

Results from Peter's 3 week "nothingburger" (1 week keto—1 week fast—1 week keto) (AMA #2)
Peter Attia MD
This hormone level was around the 50th-55th percentile at baseline and saw changes throughout the experiment.

Testosterone replacement therapy: compelling use cases, side effects, and optimal dosing schedules
Peter Attia MD
Refers to the unbound, biologically active form of testosterone, which is difficult to measure directly and is often estimated.