Medications for treatment of hypothyroidism
Hypothyroidism is a condition of decreased thyroid hormone production from the thyroid gland, which affects about 2% of the adult population in the United States.
Millions of Americans take thyroid hormone replacement medications to treat hypothyroidism. This medication works to replace the hormones patients need to maintain normal thyroid hormone levels and helps prevent or lessen symptoms of hypothyroidism, such as fatigue, weight gain, constipation, cold intolerance or depressed mood, among others.
Generally, thyroid hormone replacement medications need to be dosed very carefully. A dose that is too high or low may not produce the intended effect, may increase the symptoms of hypothyroidism or may cause side effects. This means a doctor needs to monitor a patient’s thyroid hormone levels closely and adjust their medication dose precisely to keep their levels in the right range.
Currently there are two types of thyroid hormone replacement medicines on the market, available only by prescription:
- The most commonly used type of therapy is synthetic (laboratory-made) medications containing levothyroxine or liothyronine. An estimated 22 million patients received prescriptions for levothyroxine dispensed by U.S. outpatient retail and mail-order pharmacies in 2024. These medications have been FDA-approved for decades and are marketed as branded and generic medications containing levothyroxine sodium or liothyronine sodium. Search drugs@fda for a list of FDA-approved medications.
- The second type of therapy is animal-derived thyroid medication and sometimes called desiccated thyroid extract, or DTE. These medications are marketed as Armour Thyroid, NP Thyroid, Nature-Thyroid and Natural Thyroid, among other names. These medications are produced from dried, ground animal thyroid glands (usually porcine, meaning from a pig). Animal-derived thyroid medications are not FDA approved, yet an estimated 1.5 million patients received prescriptions for these medications from U.S. outpatient retail and mail-order pharmacies in 2024. Due to their complex biological origin, these medications contain many compounds that are uncharacterized for safety and effectiveness.
Professional medical society guidelines recommend synthetic levothyroxine as the preferred treatment for hypothyroidism, with the goal of normalizing thyroid hormone levels.
FDA plans to issue draft guidance
FDA informed manufacturers, importers and distributors of marketed unapproved animal-derived thyroid medications of its intent to issue a guidance regarding the agency’s compliance priorities by August 2026. FDA is committed to ensuring safety of patients currently using unapproved animal-derived thyroid medications while manufacturers are working toward FDA approval for these medications.
FDA is currently applying its risk-based enforcement approach to unapproved animal-derived medications, and may take action. For example, the agency may take action against a manufacturer that is not meeting quality standards and putting patients at risk.
Additionally, these unapproved animal-derived thyroid medications are not eligible for compounding because these products are regulated as biological products under the Public Health Service Act.
FDA’s concerns with unapproved thyroid medications
FDA has concerns with the safety and effectiveness of unapproved animal-derived thyroid medications, because they have not been reviewed by FDA to ensure the safety, purity and potency. These medications may have quality and dosing issues. For example:
- Tablets made from the same manufacturing batches of animal-derived source material may not always provide the same thyroid hormone levels. Inconsistent doses of thyroid level hormones can have serious consequences for patients. Too much medication can cause unwanted effects, and too little may not be effective.
- Unapproved thyroid medications have an increased risk of certain impurities due to the source – animal thyroid glands – or the way it is manufactured. These issues can lead to infections and other health concerns.
The agency has received complaints from patients and reports of adverse events related to the safety and potency of these unapproved medications.
FDA recommendations for patients
FDA is committed to ensuring safety of patients currently using unapproved animal-derived thyroid medications while manufacturers are working toward FDA approval for these medications.
The agency continues to recommend patients taking unapproved animal-derived thyroid medications to treat hypothyroidism talk to their doctor. Your primary care doctor or a professional medical society, such as the Endocrine Society or the American Association of Clinical Endocrinologists, can help identify an experienced endocrinologist, which is a specialist who supports patients with thyroid and other hormone disorders.
The Endocrine Society, American Thyroid Association (ATA) and American Association of Clinical Endocrinologists (AACE) provide information about hypothyroidism and its treatment on their websites for patients and health care providers.
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