There is no cure to Cushings Disease, but if you diagnose it quick, there are medications they can be on so they can still be in normal health for the rest of their life. Discontinuing the medication will result in the cushings symptoms appearing.
We had a horse (died) at our barn with cushing (she coliced really bad, that's what killed her) we had to give her medicine 3 X a week..
She also got LOTS of hair, It grew like 5 inches and she could not shed it out. (the medicine helped shed some out.) We finally body clipped her but everything Anni and Mary (Skippy) have said are correct.