Eustatia-Rutten CFA et al. (2006) Quality of life in longterm exogenous subclinical hyperthyroidism and the effects of restoration of euthyroidism, a randomized controlled trial. Clin Endocrinol 64: 284–291

A Dutch team has reported on the effects of restoring euthyroidism in patients with subclinical hyperthyroidism due to long-term TSH-suppressive therapy after treatment of differentiated thyroid carcinoma (DTC).

In total, 24 patients with a history of DTC who had undergone >10 years' TSH-suppressive therapy completed the trial. Half of these patients continued their existing TSH therapy (low-TSH group), while the other half were given decreasing doses of levothyroxine, thereby restoring euthyroidism (euthyroid group). All participants completed five questionnaires, which assessed different aspects of quality of life (QOL), at baseline and at 6 months. Surprisingly, baseline symptoms of hyperthyoidism were not different from reference values; however, SOMATOFORM DISORDER scores were markedly higher than reference values.

Contrary to the investigators' expectation of improved QOL scores at 6 months, most of the results for the euthyroid group were comparable to their baseline scores. The only significant changes were in two of the questionnaires: in one of five parameters of fatigue, and in one of eight parameters of general well-being.

The authors caution that their results are difficult to compare with the findings of previous studies. The experience of having survived DTC might improve perceived quality of life, counterbalancing any negative effects of subclinical hyperthyroidism. The baseline depression scores of both groups were significantly better than those of the general population; further, hyperthyroid symptom scores were no higher than those of controls. Overall, these results indicate that the relationship between subclinical hyperthyroidism, symptoms, and QOL is complex.