Can minoxidil responders be predicted?

What determines who is a responder and who is not? Is it the amount of sulfotransferases in the scalp or something else? I always assumed those who don’t respond to the topical version will respond to the oral because the liver has more of these enzymes which will convert the minoxidil to minoxidil sulfate.

There are tests that can tell you if you will respond to topical minoxidil.  Minoxidil has to be converted to an active form by sulfotransferase enzymes that may or may not be present in sufficient quantities in hair roots. When the drug is taken orally, it is automatically converted to an active form so if it is taken orally, the response is much, much higher.