The American Association of Clinical Endocrinology (AACE) recognizes that desiccated thyroid extract (DTE) has been available to patients since the late 19th century and is considered a “grandfathered” therapy, existing prior to the implementation of modern U.S. Food and Drug Administration (FDA) approval requirements. These medications are produced from dried and ground animal thyroid glands, most commonly sourced from pigs (porcine). Although DTE is widely prescribed, it currently does not have FDA approval. In 2024, approximately 1.5 million patients received prescriptions for DTE from U.S. outpatient retail pharmacies. Because of their complex biological origin, these medications contain numerous compounds that are uncharacterized for safety and effectiveness under current regulatory standards.

AACE, together with other leading professional medical societies and as recognized by the FDA, recommends levothyroxine as the primary treatment for hypothyroidism. This position is based on extensive evidence demonstrating that levothyroxine offers reliable safety, efficacy, and predictable dosing, which helps patients achieve stable and normalized thyroid hormone levels. The FDA has specifically referenced AACE as a reliable source of information in its guidance regarding thyroid hormone therapy.

While levothyroxine is recommended as the first-line therapy for most patients, AACE strongly supports equitable access and the principles of personalized medicine. DTE remains an alternative therapy that can be considered for select patients based on clinical judgment and individualized, evidence-based discussion between patients and their healthcare providers.

Recently, the FDA announced that all animal-derived thyroid products, including DTE, must now undergo the biologics license application (BLA) process to remain on the U.S. market. This process requires manufacturers to submit detailed clinical and quality data demonstrating product safety, potency, and consistency. The FDA is permitting a transition period and encouraging patients and clinicians to consider FDA-approved alternatives, while acknowledging that awareness about these regulatory changes may still be limited within the patient and provider communities.

AACE remains committed to advocating for equitable access to all safe and effective thyroid therapies. AACE supports a balanced regulatory approach that upholds the highest quality standards and ensures patient treatment choices are not unnecessarily limited. AACE believes ongoing collaboration among the FDA, healthcare providers, patients, and industry partners is essential for delivering optimal, individualized thyroid care for everyone.

Malini Gupta, MD, FACE, ECNU
Chair, AACE Thyroid Disease State Network

Scott Isaacs, MD, FACP, FACE
AACE President