Most doctors recommend levothyroxine, the synthetic form of thyroxine (T-4). However, natural extracts are available that contain thyroid hormone derived from the thyroid glands of pigs. These products — Armour Thyroid, for example — contain both levothyroxine and triiodothyronine.
Doctors have a number of concerns about natural thyroid hormone extracts such as Armour Thyroid, including:
- The balance of T-4 and T-3 in animals isn't the same as in humans.
- The exact amount of T-4 and T-3 in each batch of a natural extract product can vary, leading to unpredictable levels of these hormones in your blood.
- T-3 is more potent than T-4, so even a mild excess could cause problems.
Still, researchers have investigated whether adjusting standard hypothyroidism treatment to replace some T-4 with T-3 may offer benefit. The majority of studies have determined that the addition of T-3 does not offer any advantage over treatment with T-4 alone.
However, there is some evidence that T-3 may offer benefit to certain subsets of people, such as people who have had their thyroid surgically removed (thyroidectomy). Research is ongoing.
Jan. 02, 2014
- Davies TF. Pathogenesis of Hashimoto's thyroiditis (chronic autoimmune thyroiditis). http://www.uptodate.com/home. Accessed Oct. 7, 2013.
- Frequently asked questions: Hashimoto's disease. Office on Women's Health. http://www.womenshealth.gov/publications/our-publications/fact-sheet/hashimoto-disease.cfm. Accessed Oct. 7, 2013.
- Hashimoto's thyroiditis. American Association of Clinical Endocrinologists. http://www.thyroidawareness.com/hashimotos. Accessed Oct. 7, 2013.
- Ross DS. Disorders that cause hypothyroidism. http://www.uptodate.com/home. Accessed Oct. 7, 2013.
- Garber JR, et al. Clinical practice guidelines for hypothyroidism in adults: Cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Endocrine Practice. 2012;18:988.
- Ross DS. Treatment of hypothyroidism. http://www.uptodate.com/home. Accessed Oct. 7, 2013.
- Nippoldt TB (expert opinion). Mayo Clinic, Rochester, Minn. October 7, 2013.
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