One of my past dogs was on thyroxine for a while. I eventually discovered thytrophin PMG. It is bovine thyroid extract and maybe some other stuff. I started by cutting back on the thyroxine and adding the PMG. After I had her on it for a little bit (guessing a dosage), I had her blood tested several times over a period of time. It actually seemed to regulate her thyroid levels better. You may want to look into it. It is made by Standard Process. I got the kind made for humans. When I did buy it (has been a few years), spinelife.com seemed to have the lowest prices, but go onto standard process' website to get lots of information on the product. I highly recommend it.