When the thyroid is underactive (hypothyroidism) due to autoimmune disease (Hashimoto's disease), radioactive iodine treatment, congenital defects, or surgical removal (thyroidectomy), the key medical treatment is thyroid hormone replacement with a prescription medication.
The following is an overview of the key thyroid hormone replacement medications.
Levothyroxine (Synthetic Thyroxine/T4)
Among conventional physicians, the most popular and commonly prescribed thyroid hormone replacement drug is levothyroxine, a synthetic form of thyroxine (the thyroid hormone abbreviated as T4). Levothyroxine is also referred to as l-thyroxine.
In the United States, levothyroxine is available as generic levothyroxine, as well as Synthroid, Levothroid, and Levoxyl brand name tablets of levothyroxine. Tirosint is a liquid gelcap form of levothyroxine that has been on the market since 2011.
In Canada, Synthroid, Eltroxin, and PMS-Levothyroxine are popular brand names.
Many doctors do not recommend generic levothyroxine. Brand names are preferred, and each is generally considered equally effective.
Liothyronine (Synthetic Triiodothyronine/T3)
The thyroid gland manufacturers both thyroxine and triiodothyronine (T3), the active form of thyroid hormone. Liothyronine is a synthetic form of T3, and it is available in a manufactured form as the brand Cytomel, and also as generic liothyronine. T3 can also be compounded.
In recent years, some practitioners have been prescribing T3 in addition to T4. One 2009 study showed that the majority of patients preferred levothyroxine plus T3 compared to levothyroxine-only treatment.
A prominent study published in the New England Journal of Medicine found that patients benefited from T4/T3 combination treatment. Some other studies have failed to demonstrate a benefit and the use of T4/T3 combination treatments remains controversial.
Liotrix (Synthetic Thyroxine/Triiodothyronine T4/T3 Combination)
Liotrix is a synthetic combination of thyroxine and triiodothyronine (T4 and T3). Liotrix is available in a manufactured form, known by the brand name Thyrolar, manufactured by Forest Labs. Thyrolar has been in back-order and short supply for a number of years, and is rarely used in the United States.
Desiccated Natural Thyroid
Desiccated thyroid is a drug prepared from dried porcine (pig) thyroid. Desiccated thyroid was the only thyroid drug available in the early 1900s, until levothyroxine was introduced in the 1950s. Natural thyroid fell out of favor as the synthetic product was touted as more modern and stable. Since the 1990s, desiccated thyroid has enjoyed a resurgence, primarily with older doctors and holistically-oriented physicians who claim that it resolves symptoms better than synthetics in some patients.
Today, several brands of desiccated thyroid are available by prescription, including Nature-Throid, Wes-throid, Armour Thyroid, and a Canadian natural thyroid from manufacturer Erfa.
SourcesBraverman, MD, Lewis E., and Robert D. Utiger, MD. Werner and Ingbar's The Thyroid: A Fundamental and Clinical Text. 9th ed. Philadelphia: Lippincott Williams & Wilkins (LWW), 2005.
Shomon, Mary. Living Well With Hypothyroidism: What Your Doctor Doesn't Tell You...That You Need to Know. 2nd ed. New York. HarperCollins. 2005.