When your hypothyroid symptoms return after you have been optimal for a while on a certain brand of thyroid hormone, it is important to look for the underlying causes or changes in the thyroid medication market. As I help so many people feel better, I also learn from my patients what works and what does not work. Well, in the light of recent changes in the production of NP Thyroid and Nature-Throid I have to look for a different type of thyroid medication for myself and my patients.