Muscle performance and postural stability are reduced in patients with newly diagnosed Graves' disease.

BACKGROUND: Reduced muscle strength is an acknowledged symptom of Graves' disease, but our knowledge on severity is sparse. We aimed to investigate muscle strength, balance, and muscle function in patients with Graves' disease compared to age- and gender-matched healthy controls.

METHOD: Using a cross sectional design, we compared 55 patients newly diagnosed with Graves' disease with 55 euthyroid controls, matched on sex, age, and menopausal status. We measured isometric muscle strength (Newton) and maximum force production (Newton/second) across different muscles groups using a dynamometer chair and postural stability (balance) in different positions using a stadiometer. Muscle function was assessed using the Timed-Up-and-Go test and the Repeated Chair Stand test.

RESULTS: Patients and controls were well matched. Handgrip maximum muscle strength as well as strength at elbow and knee flexion and extension were significantly impaired in patients compared to controls. Maximum force production was only significantly reduced at elbow flexion. Patients performed the Timed-Up-and-Go- and the Repeated Chair Stand-test significantly slower than controls and postural stability was significantly reduced in patients compared to controls in all positions. Free triiodothyronine (T3) correlated with reduced muscle strength and postural stability.

CONCLUSION: At time of diagnosis, Graves' disease is associated with impaired maximum muscle strength, performance, and balance, whereas maximum force production is overall comparable to euthyroid controls. .