Compounded hormone therapy uses bioidentical hormones that are derived from plant sources to identically match the structure of human hormones, making it a much more natural approach to hormone therapy. Bioidentical hormones are estradiol, estriol, and progesterone. Any additions to these words and you have a non-bioidentical product.
Non-compounded hormone therapy does not usually involve bioidentical hormones. Things like Premarin (derived from the pregnant horses), ethinyl estradiol, progestins (norethindrone, medroxyprogesterone, and a host of others) are all not bioidentical and made only to work on specific receptors. Your body has hormone receptors all over, when these non-bioidentical hormones attach to receptors other than where they were studied to work, there is no telling what havoc they will cause. If you get your hormones in a small 21 or 28 day pack, you can almost be sure that you are not receiving all bioidentical hormones.