Thyroid Research Thyroid Research Archive Hypothyroidism

Thyroxine alone is as effective as triiodothyronine plus thyroxine in improving symptoms and cognitive function in hypothyroid patients

(March 2004)

The background of the study. Many patients with hypothyroidism do not feel well despite adequate thyroxine (T4) therapy. This study compared the effect of thyroxine (T4) and triiodothyronine (T3) therapy with T4 therapy alone in unselected patients with hypothyroidism.

How the study was done. Forty-four patients (36 women) with hypothyroidism were recruited by advertisements inviting them to participate in a study of treatment of hypothyroidism. All had been treated for at least six months, with no change in dose in the past three months; their mean daily dose of T4 was 128 µg. The patients were randomly assigned to receive their usual dose of T4 or their usual dose of T4 less 50 µg once daily and a capsule containing 7.5 µg of T3 twice daily for four months. The patients were evaluated using a health-related quality of life (HRQL) questionnaire for hypothyroidism; standardized tests of cognitive function, and the Beck Depression Inventory at base line and at the end of treatment.

The results of the study. During the four-month treatment period, there were no changes in weight, heart rate, blood pressure, or serum thyrotropin in either group, but the serum free T4 concentration decreased in the T4-plus-T3 group. The hypothyroid HRQL scores decreased in both groups, and the decreases were similar in magnitude in both groups. There were no differences in the scores on the tests of cognitive function or the Beck Depression inventory in the two groups either at base line or at the end of the study.

The conclusions of the study. In patients with hypothyroidism, T4 plus T3 and T4 alone have similar effects on symptoms of hypothyroidism and tests of cognitive function or depression.

The original article. Clyde PW, Harari AE, Getka EJ, Shakir KM. Combined levothyroxine plus liothyronine compared with levothyroxine alone in primary hypothyroidism: a randomized controlled trial. JAMA 2003;290:2952-8.