like many "androgenic" substances they all end up suppressing some aspect of the system and homeostasis will be fucked 
Ive seen a lot of little skinny twinks totally suppress their estrogen after a few weeks of a certain popular SARM - they get depressed, can't grow , no appetite 
and I didn't know they were "legal" - I know the IOC has banned them, same as UFC they test for them too 
I guess if your a basic bitch gym Twink they are "legal"