For years the FDA has wanted natural thyroid replacement off the market. Now the agency is moving to eliminate individualized versions of this medicine. Action Alert! The FDA has declared natural desiccated thyroid (NDT) to be a “biologic” and thus ineligible for pharmacy compounding. This is the latest in a decades-long effort by the agency to remove natural thyroid medicines from the market in favor of FDA-approved thyroid drugs that many patients cannot use. Read more.