Ten years ago Armour was great, then they changed the ingredients slightly, it was because the way the tablet was pressed or something, and patients complained that they felt hypothyroid on the same dose. Many changed over to Nature Thyroid brand, and it was wonderful for years. Now Nature Thyroid the last couple of years is made by another company and patients complain about it as well (that it doesn't work). Meanwhile the Thyroid-S has always been the same. But don't take my word for it, Stop The Thyroid Madness is the authority on thyroid meds, treatment, etc. Thyro-Gold is also good, but it's more expensive.