Is All Levothyroxine Porcine-Based?
No, levothyroxine is not porcine-based—it is synthetically manufactured thyroxine (T4) hormone, not derived from animal sources. 1, 2
Understanding Levothyroxine vs. Desiccated Thyroid
Levothyroxine is artificially manufactured thyroxine used as a drug to treat hypothyroidism, and it is the standard of care recommended by all major endocrine societies. 1, 2
- Levothyroxine monotherapy has emerged as the therapy of choice in all recent major guidelines for treating hypothyroidism 2
- The drug is synthetically produced in pharmaceutical facilities, not extracted from animal thyroid glands 1, 2
The Confusion with Desiccated Thyroid Products
Desiccated thyroid preparations, which ARE porcine or bovine-based, are completely different products from levothyroxine. 3
- Desiccated porcine or bovine thyroid products contain actual animal thyroid tissue and are sometimes found in nutritional supplements sold in health food stores 3
- These animal-derived products are largely unregulated by the FDA when marketed as nutritional supplements 3
- Desiccated thyroid products can contain unpredictable doses that may exceed normal replacement doses by two to three times, potentially causing hyperthyroidism 3
Clinical Implications
Physicians have used thyroid hormone replacement for over 130 years, with animal thyroid-derived preparations being the historical treatment, but synthetic levothyroxine has replaced these older formulations in modern medical practice. 2
- Ingestion of animal thyroid-derived preparations has been scientifically documented for the last 130 years, but pharmaceutical production and regulation have continuously refined to favor synthetic preparations 2
- Studies of thyroid hormone metabolism, action, and pharmacokinetics have led to focused recommendations favoring synthetic levothyroxine over animal-derived products 2
Important Caveat
Patients taking "thyroid supplements" from health food stores may unknowingly be consuming desiccated animal thyroid rather than pharmaceutical-grade synthetic levothyroxine, which poses significant safety risks. 3