https://www.pbs.org/wgbh/nova/next/bo...-last-decades/

"Physiologists from the University of Oslo in Norway have been studying the effects of anabolic steroids in mice, and their findings suggest that the boost the substances give to muscles could last for decades. The substances appear to give muscles a sort of memory that allows them to bulk up rapidly when stressed even long after they’ve been withdrawn.

In a study, researchers gave female mice an anabolic steroid, testosterone propionate, for 14 days. In that time, the mice’s muscles bulked up significantly, adding 77% more girth and 66% more myonuclei. After the steroids were withdrawn for three months (about 10% of the mouse’s lifespan), the mice’s muscles lost bulk but not myonuclei. The researchers then started the mice on an intensive exercise regimen for six days, though this time without any steroids. Non-doped mice didn’t see their muscles grow significantly in that time, but the formerly ’roided mice added 31% more cross-sectional muscle area."