The use of T4 and T3 together as a thyroid hormone replacement treatment for hypothyroidism -- an underactive thyroid -- is controversial, given that the standard treatment is levothyroxine (T4) alone. The addition of T3 to the levothyroxine/T4-only treatment is, however, a topic of ongoing research and discussion. This treatment controversy is explored in a number of articles here at the About.com Thyroid site.
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A 1999 study reported in the New England Journal of Medicine found that patient quality of life was improved with the addition of T3 to levothyroxine therapy.
The Journal of the American Medical Association (JAMA) reported on research that found no benefit to the addition of T3.
Dr. Ken Woliner critiques the 2003 JAMA study and points out problems in the study, suggesting that T3 should not be ruled out based on the study's findings.
Dr. Ken Blanchard, MD, PhD, author of the book "What Your Doctor May Not Tell You About Hypothyroidism," critiques the 2003 JAMA study.
Chronic fatigue, fibromyalgia and metabolism expert Jacob Teitelbaum, MD has these criticial insights about the JAMA T4/T3 studies.
The results of trial published in the March 2005 Archives of Internal Medicine compared levothyroxine/T4 treatment for hypothyroidism, versus 2 different combinations of levothyroxine plus synthetic T3 (known as liothyronine).
The May 2005 issue of the Journal of Clinical Endocrinology and Metabolism reported on a study that showed that hypothyroidism patients preferred a combination T4/T3 treatment to T4-only treatment. The researchers also found that combination treatment is associated with weight loss, while T4-only treatment is not.