Hypothyroidism Drugs: Treating an Underactive Thyroid

Guide to Prescription Thyroid Hormone Replacement Drugs

The thyroid can be underactive – a condition known as hypothyroidism – due to autoimmune Hashimoto's disease, certain medications, or other issues. Radioactive iodine treatment for Graves' disease and hyperthyroidism can leave the thyroid underactive – or completely shut down. In some cases, surgical removal (thyroidectomy) is performed as a treatment for thyroid cancer, a goiter (enlarged thyroid), or less commonly, hyperthyroidism. In some cases, infants are born with a missing or malfunctioning thyroid – a condition known as congenital hypothyroidism.

In all cases, the treatment for an underactive thyroid, shut down gland, surgically removed gland or congenitally damaged gland is thyroid hormone replacement with a prescription thyroid drug. 

The following is an overview of the key thyroid hormone replacement medications.

Levothyroxine (Synthetic Thyroxine/T4)

Prescription Medication Medicine Pill Tablets
EH Stock/E+/Getty Images

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, and L-T4.

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 brand is generally considered equally effective.

Liothyronine (Synthetic Triiodothyronine/T3)

Pill bottle with pills
TEK IMAGE/Getty Images

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.

A new time-released synthetic T3 drug, Thyromax, is in clinical trials and is being evaluated for potential approval and distribution in the U.S. 

Desiccated Natural Thyroid

Natural desiccated thyroid – sometimes abbreviated NDT – is a drug prepared from dried porcine (pig) thyroid glands. Natural desiccated thyroid was the only thyroid drug available in the early 1900s, under the brand name Armour Thyroid, 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, however, desiccated thyroid has enjoyed a resurgence, primarily with older doctors familiar with the drug, and holistically-oriented and integrative physicians who claim that it resolves symptoms better than synthetic thyroid drugs in some of their patients.

Today, several brands of desiccated thyroid are available in the U.S. and in some other countries, by prescription, including Naturethroid, WP Thyroid, Armour Thyroid, a generic NP Thyroid (made by manufacturer Acella), and a Canadian natural thyroid from manufacturer Erfa.

Liotrix (Synthetic Thyroxine/Triiodothyronine T4/T3 Combination)

Liotrix was a synthetic combination of thyroxine and triiodothyronine (T4 and T3). In recent years, liotrix was available in a manufactured form, known by the brand name Thyrolar, from Forest Labs. But Thyrolar has been off the market for a number of years, and is no longer available or used. 


Braverman, 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.