Use T:epiT ratio + pituitary suppression markers to detect exogenous testosterone
Attia explains this in response to Schaap's question about why Lance Armstrong was not caught earlier while using EPO, pivoting to explain why testosterone — despite being more physiologically potent — is actually more detectable than EPO and HGH. The practical implication for longevity-oriented readers: men on TRT who are also competitive athletes should understand that their protocol will produce a detectable signature, and that off-label cycling of testosterone can be identified by the LH/FSH suppression pattern even when T levels appear normal at the time of testing.
Exogenous androgen activates hypothalamic-pituitary negative feedback, suppressing GnRH → LH → FSH axis. Epi-testosterone is a constitutional byproduct of endogenous production, not co-released from exogenous sources — so the ratio diverges.
You can look for epi testosterone and if that's not rising at the levels of testosterone you know they're taking it and you can look at other hormones that get suppressed when you take testosterone so if you're taking testosterone exogenously from outside the body the pituitary hormones that tell the body to make it luteinizing hormone follicle stimulating measurement they go down.

