Hypothyroid? Will You Benefit From T3 (Cytomel)?

Over 20 years ago endocrinologists had experience with hormone compound pills containing both T4 and T3.

Those physicians who had the opportunity to use these compounds know that patients frequently seem to do better with them than with the more traditional T4 (Synthroid, L-thyroxine, Levoxyl etc.). For various reasons most companies stopped producing combination thyroid hormone pills two decades ago.

Why does combination therapy with T4 and T3 appear to provide more benefits than either hormone alone? The reason was clarified in an article published in The New England Journal of Medicine summarized in this news report;

NEW YORK, Feb 10 (Reuters Health) - Patients with hypothyroidism show greater improvements in mood and brain function if they receive treatment with two types of thyroid hormones instead of one, according to a report in the February 11th issue of The New England Journal of Medicine.

Hypothyroidism, where the gland has ceased to function or has been removed, is usually treated with daily doses of thyroxine hormone. But the researchers found that substituting another thyroid hormone, triiodothyronine, for some of the thyroxine dose led to improvements in mood and in neuropsychological functioning.

"There are two thyroid hormones, thyroxine and triiodothyronine," Dr. Robertas Bunevicius, of Kaunas Medical University in Lithuania, and colleagues explain in their paper.

"Not all tissues that need thyroid hormone are equally able to convert thyroxine to triiodothyronine, the active form of the hormone," the researchers write. "Nevertheless, most patients with hypothyroidism (reduced thyroid function) are treated only with thyroxine."

Currently Cytomel is made by different pharmaceutical companies under different trade names. Triidothyronine (Liothyronine) represents a preparation of thyroid gland hormone similar to natural thyroid hormone - liothyronine which is produced and released by thyroid gland. Triidothyronine compensate the deficiency of thyroid hormone T3. Cytomel increases the demand of tissues in oxygen, stimulates growth and their differentiation, increases the levels of basal metabolism (proteins, lipids, carbohydrates). In low doses Triidothyronine exerts anabolic action, in high doses - catabolic. In high doses Triidothyronine inhibits the production of thyrotrophin. Triidothyronine enhances energetic processes, regulates and maintain the functional activity of cardiovascular system, liver and kidneys. The effect of Cytomel is mor expressed that levothyroxine. It is indicated especially in those cases when the results of treatment should be achieved with fast-acting thyroid gland hormone with short period of action. As in hypothyroidism the processes of absorption are usually disturbed, the application of Triidothyronine is especially reasonably at the first stage of treatment. The medication starts acting in 4-8 hours. Maximal therapeutic effect is observed in 2-3 days.

To determine whether patients would benefit from receiving Cytomel as well, Bunevicius' team studied 31 women and 2 men who lacked a functioning thyroid and were dependent on thyroxine.

The research team divided the study into two 5-week sessions. During one session, each patient took his or her usual dose of thyroxine. During the other session, the researchers replaced 50 micrograms (mcg) of the thyroxine dose with 12.5 mcg of triiodothyronine.

On 6 of 17 measures of mood and cognition - a catchall term that refers to language, learning and memory - the patients scored better after receiving thyroxine plus triiodothyronine than after receiving thyroxine monotherapy.

No score was better after monotherapy than after combination treatment, the study group determined. The authors also detected biochemical evidence that "thyroid hormone action was greater after treatment with thyroxine plus triiodothyronine." But in an editorial, Dr. Anthony D. Toft, of the Royal Infirmary, Edinburgh, Scotland, recommends that physicians should not use thyroxine and triiodothyronine in combination until the study findings are confirmed by additional research.

Toft notes that "most, if not all, of the currently available combined preparations of thyroid hormones contain an excess of Cytomel as compared with thyroxine." Besides, he argues, the majority of patients taking thyroxine "have no complaints about their medication."