Do steroid effects last after you stop?

Short answer

Most of the muscle goes; the traces and side effects stay. Only about a quarter of the gained muscle remained 3 months after stopping, but muscle cell nuclei were still higher 4 years later, and low testosterone and weaker heart function showed up years later.

Do steroid effects last after you stop?
'Muscle built once stays put' — does this hold?
Some say muscle built on steroids stays after you quit; others say it all disappears. We split it into muscle, traces inside the muscle, hormones, and the heart to check what is left after stopping.
How much of the gained muscle stays?
Up 4.4 kg, only 1.2 kg left after 3 months
A study followed 79 people who planned to use the drugs on their own (median 10 weeks of use). During use, lean mass (muscle and everything except fat) rose 4.4 kg, but 3 months after stopping only 1.2 kg remained. That is about 1/4 of the gain.
So nothing stays inside the muscle?
Muscle cell nuclei were still higher 4 years later
7 people who had stopped an average of 4 years earlier had more tightly packed nuclei in their thigh muscle cells than 10 non-users, and the gap grew with longer use. Mice given the drug for 14 days and loaded 3 months later grew muscle fibers 31% thicker in 6 days. Mice never given the drug did not grow meaningfully.
Muscle is not the only thing that stays
Testosterone was still low 2.5 years later
33 people who had stopped an average of 2.5 years earlier had lower testosterone than 30 non-users, like 100 dropping to 77. 27% were below the normal range, and low sex drive (40%), erection problems (27%), and depressive symptoms (24%) were more common than in current users or non-users.
Hormones coming back is not the end
Only half of 641 people returned to normal
Of 641 people tested within 36 months of stopping, 48.2% had all reproductive hormones back to normal. 72 people less than 1 year out had testosterone no different from non-users, yet scored worse on mood, anxiety, sexual function, and quality of life.
The heart keeps a trace too
Those who quit had hearts as weak as current users
33 people who had stopped an average of 30 months earlier scored worse than 30 non-users on a measure of how strongly the heart muscle squeezes. In a study of 101 people, the share whose heart pumped out 40% or less of its blood was 10% among current users and 11% among those who had quit more than 1 year earlier.
Bottom line: the muscle goes, the traces and side effects stay
About 3/4 of the gained muscle was gone within 3 months
3 months after stopping, only about 1/4 of the gained muscle remained. But muscle cell nuclei were still higher 4 years later, and low testosterone and weaker heart function lasted for years. What stays long after quitting is less the look and more the traces and side effects inside the body.