Last summer I experienced severe depression, was tested, and found out I was hypothyroid. My doctor prescribed WP Thyroid (bovine-derived), and I was completely back to normal in just a month, with NO side effects, except for finally feeling normal. Recently, my bloodwork indicated low thyroid again, and I was told that WP is no longer available!!! I panicked but found NP Thyroid which is also a bovine source. I feel it's really important to have natural sources/help for the thyroid, given the numerous stories I hear from my friends who are taking synthroid -- each one of them experiencing extreme frustration because consistent levels are almost impossible to achieve. Medicine is an art, and patients should have a variety of ALL options!