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Combined thyroxine and triiodothyronine therapy is not more effective than thyroxine alone in patients with hypothyroidism (I)
The background of the study. Patients with hypothyroidism
are usually treated with thyroxine (T4), the major thyroid hormone.
However, they may not feel well. This study evaluated the effect
in patients with hypothyroidism of treatment with T4 alone and with
two combinations of T4 and triiodothyronine (T3), which is also
produced by the thyroid gland.
How the study was done. The study subjects were 141 patients with hypothyroidism who had been taking T4 and had normal serum thyrotropin (TSH) concentrations. They were assigned, in random order, to receive T4 alone, T4 and T3 in a ratio of 5:1, and T4 and T3 in a ratio of 10:1 for 15 weeks. In the combination-therapy groups, the daily T4 dose was reduced by 25 µg and T3 was added in the dose needed to yield the 5:1 or 10:1 ratio of T4 to T3. The primary end point was the patient’s subjective assessment of well-being at 15 weeks, graded on a five-point scale (much better to no different to much worse), as compared with their previous T4 regimen. The patients also completed questionnaires about mood, fatigue, quality of life, cognitive function, and verbal learning.
The results of the study. A total of 130 patients (92 percent) completed the 15-week study. The preference for therapy increased with increasing T3 content of the regimen. As compared with their previous T4 therapy, the study therapy was preferred by 29 percent of the patients in the T4-alone group, 41 percent in the 10:1 T4–T3 group, and 52 percent in the 5:1 T4–T3 group. The scores for the tests of mood, fatigue, quality of life, cognitive function, memory, and verbal learning improved in all three groups, with few between-group differences.
The patients in the T4-alone group gained 0.1 kg, those in the 10:1 T4-T3 group lost 0.5 kg, and those in the 5:1 T4–T3 group lost 1.8 kg. The median serum TSH concentrations in the respective groups at the end of the study were 0.64, 0.35, and 0.07 mU/L, indicating the presence of hyperthyroidism in the 5:1 T4–T3 group.
The conclusions of the study. Patients with hypothyroidism preferred combined T4 and T3 therapy, especially when the T4:T3 ratio was 5:1. This dose was associated with weight loss and low serum TSH concentrations, but not with greater improvement in mood, quality of life, and cognitive function.
The original article. Appelhof B, Fliers E, Wekking EM, Schene AH, Huyser J, Tijssen JG, Endert E, van Weert HC, Wiersinga WM. Combined therapy with levothyroxine and liothyronine in two ratios, compared with levothyroxine monotherapy in primary hypothyroidism: a double-blind, randomized, controlled clinical trial. J Clin Endocrinol Metab 2005;90:2666-74.
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| Thyroid Digest Index | | | July 2005 Thyroid Digest |
