If the problem is primarly excess estrogen from HRT then your doctor should defintely have you on aromasin preferrably, imo, but most commonly arimidex.
Now if your on HRT and you arent experiencing NEGATIVE estrogen side effects and your estrogen is in range on blood work, BUT you want to take something natural for the general health reasons then try out I3C, dim, or a combo of both @ 200mg of each 2x/day or 400mg once day I wouldnt even have a problem saying you could go up to 600mg of either one a day. I3C or Dim are great staples for men to take daily in an effort to combat all of the bad estrogens that build up in our body due to the modern enviroment, life style, toxins, processed foods, etc whether on exogenous hormones or not. Just remember I3C and dim dont stop estogen from being produced they pull estrogen floating around out of the body and there is some small evidence I3C acts on the receptor in breast tissue similar to nolvadex.
But definnately look into my personnal favorite natural anti E, SNS inhibit E. There is even a possibilty it could lower estrogen on HRT, if it isnt to bad, as it does contain an AI (as abieta acid) along side I3C @400mg a serving...