The FDA has raised significant safety concerns about unapproved animal-derived thyroid medications that approximately 1.5 million Americans currently take to treat hypothyroidism. These medications, marketed under brand names like Armour Thyroid, NP Thyroid, and Nature-Thyroid, are made from dried, ground animal thyroid glands (usually from pigs) and have never received FDA approval, despite being widely prescribed and purchased. The agency is now taking enforcement action and has informed manufacturers that it intends to issue guidance about compliance priorities by August 2026. What Makes These Medications Different from FDA-Approved Options? Currently, two types of thyroid hormone replacement medications exist on the market. The first and most commonly used type is synthetic, laboratory-made medications containing levothyroxine or liothyronine. An estimated 22 million patients received prescriptions for levothyroxine from U.S. outpatient retail and mail-order pharmacies in 2024 alone. These synthetic medications have been FDA-approved for decades and are available as both branded and generic options. The second type is animal-derived thyroid extract, or DTE, which comes from actual animal thyroid tissue. Unlike the synthetic options, these medications are not FDA-approved. Professional medical society guidelines, including those from the Endocrine Society and the American Association of Clinical Endocrinologists, recommend synthetic levothyroxine as the preferred treatment for hypothyroidism because it allows doctors to normalize thyroid hormone levels more precisely. Why Is the FDA Concerned About Safety and Potency? The FDA's concerns center on several critical issues that arise from the complex biological origin of animal-derived thyroid medications. Because these medications contain many uncharacterized compounds, they have not been reviewed by the FDA to ensure safety, purity, and potency. This creates real risks for patients who depend on consistent, reliable dosing. The most significant problem is dosing inconsistency. Tablets made from the same manufacturing batches of animal-derived source material may not always provide the same thyroid hormone levels. This inconsistency matters enormously because thyroid hormone replacement requires very careful dosing. A dose that is too high or too low may not produce the intended effect, may increase symptoms of hypothyroidism, or may cause unwanted side effects. Doctors need to monitor patients' thyroid hormone levels closely and adjust medication doses precisely to keep levels in the right range. Beyond dosing concerns, unapproved thyroid medications have an increased risk of certain impurities due to their animal source or manufacturing process. These issues can lead to infections and other health concerns. The FDA has already received complaints from patients and reports of adverse events related to the safety and potency of these unapproved medications. Steps to Take If You're Currently Using Animal-Derived Thyroid Medications - Talk to Your Doctor: The FDA strongly recommends that patients taking unapproved animal-derived thyroid medications speak with their doctor about their treatment options and concerns about medication consistency. - Consult an Endocrinologist: Your primary care doctor or a professional medical society such as the Endocrine Society or the American Association of Clinical Endocrinologists can help you identify an experienced endocrinologist, which is a specialist who supports patients with thyroid and other hormone disorders. - Explore FDA-Approved Alternatives: Ask your healthcare provider about switching to FDA-approved synthetic levothyroxine or liothyronine medications, which have been proven safe and effective for treating hypothyroidism and allow for more precise dosing adjustments. - Monitor Your Symptoms: Keep track of any changes in fatigue, weight gain, constipation, cold intolerance, or mood changes, and report these to your doctor so your medication can be adjusted if needed. What Happens Next with These Medications? The FDA is currently applying a risk-based enforcement approach to unapproved animal-derived medications and may take action against manufacturers that are not meeting quality standards and putting patients at risk. Additionally, these unapproved animal-derived thyroid medications are not eligible for compounding because they are regulated as biological products under the Public Health Service Act. The agency remains committed to ensuring the safety of patients currently using unapproved animal-derived thyroid medications while manufacturers work toward FDA approval. However, the timeline for approval is uncertain, and the FDA's August 2026 guidance deadline suggests the agency is moving toward stricter enforcement. For context, hypothyroidism affects about 2% of the adult population in the United States. This condition causes decreased thyroid hormone production from the thyroid gland, leading to symptoms like fatigue, weight gain, constipation, cold intolerance, and depressed mood. Millions of Americans rely on thyroid hormone replacement medications to manage these symptoms and maintain normal thyroid hormone levels. If you're currently taking an unapproved animal-derived thyroid medication, this FDA action is a good time to have a conversation with your healthcare provider about whether switching to an FDA-approved synthetic option might be right for you. The goal is to ensure you're receiving consistent, safe, and effective treatment for your hypothyroidism.
