The FDA has issued warnings to manufacturers and distributors of unapproved animal-derived thyroid medications citing concerns over safety, effectiveness and quality.  The drugs, often sold under names Armour Thyroid, NP thyroid and Natural Thyroid, are made from dried pig thyroid glands. Although they were used by around 1.5 million Americans in 2024, the drugs have not been approved by the FDA, according to an Aug. 7 news release from the agency.

The FDA said the medications may contain inconsistent hormone levels and carry a higher risk of contamination or impurities. Unlike synthetic thyroid medications, which have been FDA approved for decades, the animal-derived products have not been reviewed for safety or potency.  In letters sent Aug. 6, the agency informed companies it may take

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