Feb. 16, 1999 CHAPEL HILL - Adding a second natural hormone known as triiodothyronine to the standard treatment for patients suffering from hypothyroidism can boost mood and mental function, according to a new study.
The findings may improve the quality of life for hundreds of thousands of hypothyroidism patients in the United States alone, researchers say. Under-activity of the thyroid gland affects about 1 percent of the population.
A report on the research, conducted in Lithuania with help from a University of North Carolina at Chapel Hill researcher, appears in the Feb. 11 issue of the New England Journal of Medicine. Authors are Drs. Robertas Bunevicius, Gintautas Kazanavicius and Rimas Zalinkevicius of Kaunas Medical University in Kaunas, Lithuania, and Arthur J. Prange, professor of psychiatry at the UNC-CH School of Medicine.
"Some patients who have lost their thyroid gland to disease, surgery or injuries complain that they are not as mentally sharp as they used to be," Prange said. "They say their sense of well-being, energy, memory and various other facets of brain function have declined."
The thyroid gland produces two hormones - thyroxine, or T4, and triiodothyronine, also called T3, he explained. Traditionally, hormone replacement is limited to T4 because most body tissues can convert T4 to T3 on their own.
"We said to ourselves that perhaps the little bit of T3 that is normally secreted by the thyroid gland is important to the brain, if not to other tissues," Prange said.
Bunevicius, who worked with Prange in Chapel Hill with the aid of a Fulbright grant, and colleagues studied 33 hypothyroidism patients in Lithuania for two five-week periods. They divided the patients in half randomly, giving one group their usual dose of T4 alone and the other a reduced amount of T4 combined with T3 substitution. After the first five weeks, they reversed the treatment pattern.
When each regimen ended, they performed biochemical, physiologic and psychological tests.
"We found there wasn't much difference between the two treatments in terms of metabolic effects or effects on various peripheral organs," Prange said. "There were big differences, however, in the mental state of the patients. If these findings hold up, they will be very important."
All but two volunteers fared better in terms of memory, mood, concentration, depression, energy and other characteristics on the combined therapy, he said. When asked at the end of the study which treatment they preferred, 20 of the 33 preferred the combined therapy, 11 had no opinion and two preferred T4 alone.
About 80 percent of patients who may benefit would be women since hypothyroidism affects four women - often in the prime of life - for every man. Some patients complain of psychological symptoms, Prange said, while their endocrinologists find nothing else wrong with their thyroid function. Doctors then cannot offer further help, which increases patients' frustration.
"From this work we concluded that the small amount of T3 secreted by the normal thyroid gland may be important to the brain even if it is not very important to other tissues," Prange said.
In an accompanying editorial, Dr. Anthony D. Toft of the Royal Infirmary in Edinburgh, Scotland, wrote that doctors should not yet begin to treat hypothyroidism patients with a combination of thyroxine and triiodothyronine for several reasons.
First, Toft said, the new results should be verified in other studies, and other factors such as exercise tolerance and heart performance should be assessed. Second, combined thyroid hormone treatments now available contain excess triiodothyronine and should be changed to reflect a 10-to-1 ratio of thyroxine to triiodothyronine.
"Finally, it should not be forgotten that the majority of patients taking a dose of thyroxine that satisfies the recommendations of the American Thyroid Association have no complaints about their medication," he wrote.
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