Well I'm 40 and my T is low enough now that I could probably qualify for TRT (but I'm delaying it). My lifts are down from my prime, but a lot of that is due to injuries. I can however still squat and deadlift in the 500's. And this is still more than what a lot of "enhanced lifters" (they openly sell in my gym's bathroom) can do. So these guys are younger than me and have at least 4x my blood T levels. And I can still outlift them.
There are countless other factors to someone's strength than just T levels. Otherwise, every gym rat on roids would be smashing records from tested federations.
https://bretcontreras.com/abc-can-a-testosterone-challenged-man-still-be-muscular/
But high levels are not mandatory for muscular growth, which is why some women are able to grow larger muscles than some men despite the fact that they produce one-tenth to one-twentieth the testosterone levels of men. Here’s why:
According to research, satellite cell efficiency appears to be the most important factor in muscular growth. Some folks have efficient satellite cell systems while others don’t. Satellite cells are located between the basil lamina and sarcolemma toward the periphery of the myofibers and function like stem cells. Once a nucleus and its surrounding sarcoplasm reaches approximately 2,000 square micrometers per nucleus (or 17-25% of the fiber’s initial size), a threshold is reached and additional nuclei are required for further growth (this has been coined the “myonuclear domain”). Efficient satellite cell systems are generous with their donation of nuclei to myofibers, and they’re also very expedient at replenishing themselves so the available pool stays bountiful. Poor satellite cell systems are stingy with their nuclei and inefficient at renewing themselves.
While testosterone is indirectly related to satellite cell efficiency through increased IGF-1 production (which has been shown to activate satellite cells) and increased androgen receptor density (which has been shown to be abundant in satellite cell nuclei), it appears that mechanical tension and muscular damage (and the associated macrophage/cytokine release) are closely related to satellite cell behavior as well. Mechanical tension also stimulates growth through increased mechanogrowth factor release and activation of the Akt/mTOR pathway, which appears to be a dominant pathway leading to muscular hypertrophy.