FDA puts thyroid medications used by 1.5 million people under scrutiny: what are they?
Armor Thyroid, NP Thyroid and other treatments made from animal glands are sold by prescription in the United States, but have never been formally approved by the FDA. The agency prepares new rules and warns of possible potency and quality problems.
The United States Food and Drug Administration put the spotlight on a group of hypothyroidism medications that were prescribed to approximately 1.5 million patients during 2024.
These are treatments made from dried animal thyroid glands, generally pigs. Among the trade names mentioned by the agency are Armor Thyroid, NP Thyroid, Nature-Throid and Natural Thyroid.
Although these products have been available for years and are prescribed by health professionals, the FDA clarifies that they are not approved by the agency. This means that they did not go through the regulatory process used to verify the safety, effectiveness, purity and consistency of medicines before authorizing their marketing.
What are the thyroid medications under review?
The measure covers medications known as dried thyroid extract, or DTE. The FDA identifies, among others, the following names:
These medicines are produced from dried and ground animal thyroid glands, usually of porcine origin. They contain thyroid hormones T4 and T3, in addition to other biological components typical of their animal origin.
This review should not be confused with a general recall. The FDA did not announce that all of these drugs are defective, nor did it ask that patients stop taking them immediately.
Why the FDA is reviewing these treatments
The main concern is that the unapproved drugs were not evaluated through the formal process that determines whether a product can be manufactured consistently and whether each tablet contains the declared amount of hormone.
This is especially important in thyroid treatments because even small variations in dosage can affect the patient. An insufficient amount can leave hypothyroidism poorly controlled, while an excessive amount can cause symptoms compatible with excess thyroid hormone.
The agency warns that tablets made from the same animal raw material may not always provide the same amount of hormone. Furthermore, the complex biological origin can increase the risk of impurities.
It also points out that complaints and reports have been received related to potency, safety and availability problems, and that some products of this type have faced previous recalls for containing more or less hormone than indicated.
What change is the FDA preparing?
On March 11, 2026, the FDA informed manufacturers, importers, and distributors that it planned to publish guidance on its compliance priorities for these drugs by August.
The agency also anticipated other guidance aimed at explaining how manufacturers could develop these products and submit formal applications for approval. Until the official update consulted, the FDA continued to describe that guidance as an intended measure and had not announced a general ban or mass recall.
In practice, the review could increase pressure on manufacturers to demonstrate that their products meet modern standards of quality, safety and consistency.
The FDA indicated that as that process moves forward, it will continue to take a risk-based approach and may take action against companies that fail to meet manufacturing standards or put patients in danger.
Will Armor Thyroid and NP Thyroid be retired?
For now, the FDA has not announced a general recall of Armor Thyroid, NP Thyroid, Nature-Throid, or Natural Thyroid.
Nor did it communicate that these medications will automatically stop being sold in August. The announced action consists of preparing a regulatory policy and guiding companies towards formal approval.
The agency says it must balance monitoring unapproved drugs with the need to avoid sudden interruptions for patients who rely on them. Before ordering broad measures, he typically considers the potential impact on treatment supply and access.
How are they different from levothyroxine?
Synthetic levothyroxine is the most widely used treatment for hypothyroidism. The FDA estimates that about 22 million patients received prescriptions for levothyroxine at retail pharmacies and by mail during 2024.
Unlike animal extracts, there are FDA-approved levothyroxine products made with controlled amounts of the T4 hormone. There are also approved medications that contain liothyronine, a synthetic form of T3.
Major medical associations cited by the agency recommend synthetic levothyroxine as the preferred treatment for most patients with hypothyroidism.
That doesn't mean everyone should get the exact same medication. The decision depends on the history, analysis, symptoms and individual response of each patient.
What symptoms can an incorrect dose cause?
An insufficient dose of thyroid hormone can allow symptoms of hypothyroidism to return or worsen, such as:
An excessive amount can cause symptoms such as palpitations, nervousness, tremors, sweating, insomnia or unexpected weight loss.
These symptoms alone do not prove that there is a problem with the medication. They may also appear when the usual dosage needs adjustment, there is an interaction with foods or supplements, or the patient's health status has changed.
What patients taking these medications should do
The FDA recommends that people using animal-derived thyroid medications talk to their doctor.
They should not suspend, reduce or change them on their own. Suddenly stopping treatment may decompensate hypothyroidism and cause more risk than continuing the prescription while obtaining professional guidance.
Also convenient:
The dose of thyroid hormones must be carefully adjusted. A product switch may require new testing and monitoring, even when both medications are used to treat the same condition.
Are these medications dangerous?
It cannot be said that all of them are dangerous or that all patients who take them suffer from problems. The central point of the FDA is another: since they are not approved, the agency has not verified product by product that they meet the same standards of safety, efficacy, quality and labeling required of authorized medications.
The FDA maintains that unapproved drugs may pose risks because their manufacturing processes, formulations and labels have not undergone a full regulatory review.
