Yes you can. Why not. Remember all HRT is doing, is replacing your own hormonal production. Is not like taking a prescription for cholesterol, or depression or pain, in which case you constantly have an extra chemical in your body. In the case of HRT, there is nothing extra; there is a replacement; so if everything is under control during your HRT, and you put something else in your body like a prohormone or another steroid, yes it will alter the levels in your body and you'll have to fix them just like a 25 year old has to do. The only difference is that you don't need PCT to bring back any test production level, cause the levels are already suppled. However, You will have to probably keep taking care of things like estrogen until your carbon unit stabilize itself and the AI do its job.