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

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Abstract
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.