The aim of this study was to evaluate the fatigue perception, the muscle function, and the health-related quality of life (QoL) in subclinical hyperthyroidism (SCH) induced by levothyroxine in the treatment of differentiated thyroid carcinoma, in comparison with a group of euthyroid (EU) subjects.Patients and Methods:
A cross-sectional study with 38 SCH individuals and 54 EU subjects was performed. They were submitted to Short Form-36 and Chalder questionnaires to evaluate QoL and fatigue, respectively. The tests performed to evaluate muscle function of upper and lower limbs were: maximum quadriceps isometric strength (QS); quadriceps fatigue resistance (T50% QS), QS at 30 seconds (QS30s); quadriceps functional capacity (QFC); maximum isometric handgrip strength (HS); fatigue handgrip resistance (T50% HS), HS at 30 seconds (HS30s); and functional capacity of the shoulder.Results and Conclusions:
The SCH patients had worse muscle function, regarding HS (25.19±7.00 vs. 30.45±9.98 kgf in EU, P=0.009) and functional capacity of the shoulder (41.28±48.36 vs. 56.68±37.44 s in EU, P=0.004). The self-perception of fatigue by Chalder questionnaire (23.91±5.39 vs. 29.77±7.03, P=0.000) and the QoL in terms of functional capacity (70.20±21.57 vs. 56.25±28.79, P=0.025), physical aspects (71.42±36.44 vs. 45.83±42.88, P=0.004), pain (62.48±22.20 vs. 50.05±24.80, P=0.035), and emotional aspects (70.74±38.26 vs. 46.29±44.56, P=0.008) were also worse in SCH. In conclusion, the SCH was associated with alterations in the QoL, reduction in the muscle function of upper limbs, and higher degree of fatigue.