Diana
I believe there were concerns that the dosage levels of hormone replacement in the medications were at times inconsistant. Sometimes higher, sometimes lower. I've taken thyroid supplements for nearly 22 years, and can appreciate your concern. Both Synthroid and Levoxyl. A current and accurate thyroid test and talk with your physician should alleviate any concerns. My levels are checked every few months, and have remained consistant. I hope yours are, too!