What occurs when your thyroid gland produces too much of the hormone thyroxine?

Tom, your dog probably had HYPOthyroidism, which is not producing enough thyroxine. The pills were a thyroxine supplement. Dogs rarely get hyperthyroidism. Cats, on the other hand, will be HYPERthyroid (if there is a thyroid problem), a pills will suppress thyroxine production.

mikhawk317, I have a 10 year old golden retriever who's been on thyroid medicine for 4 years. I believe that they have the potential to share the dame diseases as humans

I had hyperthyroidism. It began with me losing weight and my left eye twitched constantly. The eye dr caught it. I had Grave disease that's associated with thyroid problems. I lost 40 lbs within a few months. I could hardly sleep, I itched from top of my head to bottom of torso. And I lost muscle. I couldn't pick up a bowling ball nor a large glass bowl to put up in my cupboard. A thyroid specialist treated it with medicine. I was thyroid free after about 6 months. My sister had to have her thyroid gland taken out. And she finds it hard to control.

My dog had it. tablets twice a day, he seemed ok with medication.

very easy question if you know the prefixes and suffixes.