Compounding pharmacies are getting the raw API from China. Some of them are getting it from FDA registered facilities in China. Some are not.

It should be more or less the same thing as the legit stuff, but it is made with a different process, with different excipients, etc. For those going the more legit route, FDA registered still does not mean FDA inspected or that the FDA has signed off on them as being a reputable manufacturer.

There has also been cases of compounding pharmacies offering reta and other unapproved peptides, resulting in the FDA sending lots of angry letters to state pharmacy certification boards.