Comparison of exercise capacity and physical activity in patients with hyperthyroidism and controls

Background: Hyperthyroidism impairs muscle mitochondrial metabolism and destroys many body systems. However, information is limited on how much physical and physiological outcomes are impaired in patients with newly diagnosed hyperthyroidism (NDH) and euthyroid. The comparison of pulmonary function, functional exercise capacity, respiratory muscle strength and endurance, physical activity levels (PAL), dyspnea, and quality of life (QoL) in patients and healthy controls was aimed. Method: Sixteen patients with hyperthyroidism (evaluated twice at new diagnosis and euthyroid state) and healthy controls were compared. Pulmonary function was evaluated with a spirometer, functional exercise capacity with a 6-min walking test (6-MWT), respiratory muscle strength with a mouth pressure device and endurance with threshold loading test, PAL with metabolic holter, dyspnea with Modified Medical Research Council (MMRC) scale, and QoL with Quality of Life in Thyroid Patients Scale (ThyPRO). Results: Six-MWT distance and respiratory muscle endurance significantly decreased, and MMRC dyspnea scale and ThyPRO scores were higher in patients with NDH and euthyroid compared to controls (p < 0.05). In addition, maximum inspiratory pressure and maximum expiratory pressure significantly decreased in patients with NDH compared to controls, and PAL was less active according to the number of steps in euthyroid patients (p < 0.05). The pulmonary function test was similar in both groups (p > 0.05). Conclusion: Exercise capacity, respiratory muscle strength and endurance, PAL, dyspnea, and QoL were affected in patients. Patients with hyperthyroidism should be evaluated at the onset of diagnosis, followed up, and referred to cardiopulmonary rehabilitation programs at the earliest. ClinicalTrials number: NCT04825964.