Quality of life in longterm exogenous subclinical hyperthyroidism and the effects of restoration of euthyroidism, a randomized controlled trial.

OBJECTIVE: The impact of prolonged subclinical hyperthyroidism on quality of life is unclear. Therefore, we evaluated quality of life in patients with differentiated thyroid carcinoma (DTC) on TSH-suppressive thyroxine therapy as a model for subclinical hyperthyroidism and we investigated whether restoration to euthyroidism affects quality of life.

DESIGN: We performed a prospective, single-blinded, placebo-controlled, randomized trial of 6 months' duration with two parallel groups.

PATIENTS AND METHODS: Twenty-four subjects with a history of differentiated thyroid carcinoma with > 10 years TSH-suppressive therapy with L-thyroxine completed the study. L-thyroxine dose was replaced by study medication containing L-thyroxine or L-thyroxine plus placebo. Medication was titrated to establish continuation of TSH suppression (low-TSH group) and euthyroidism (euthyroid group). Both groups consisted of 12 patients. We evaluated quality of life using five validated questionnaires.

RESULTS: At baseline, the somatic disorder questionnaire (SDQ) indicated more somatic dysfunction in patients as compared with reference values, whereas the depression score (HADS) revealed a better score than the reference group. All other quality of life parameters were normal. At baseline, no significant differences between the low-TSH and the euthyroidism groups were observed. After 6 months, none of the quality of life parameters in the low-TSH group was different from baseline values. In the euthyroid group, motivation was significantly improved (Multidimensional Fatigue Index-20, P = 0.003), although this parameter did not differ from the reference group at baseline. A probable worsening in role limitations as a result of physical problems (Short Form-36; P = 0.050) was observed. No improvement in the SDQ score was observed.

CONCLUSION: In summary, quality of life in patients with DTC and long-term subclinical hyperthyroidism in general is preserved. Restoration of euthyroidism in general does not affect quality of life.