Up until a few years ago it was strongly advised to not use it for too long and taper of gradually so as not to permenently shut down you thyroid. AAlfie Newman was always sited as an athlete who's thyroid was permentently damaged by long term use.
I always thought that this was an BB forum urban myth since it had no backing. I always wondered what Alfie thought about this?
Anyway, a few years ago the bro science changed and now everyone says it is ok to use however you want because your thyriod will bounce back.
But how true is this and is there any science other than "bro science" to back it up?