Thigh muscle stiffness assessed with magnetic resonance elastography in hyperthyroid patients before and after medical treatment.

PURPOSE To measure the stiffness of the vastus medialis (VM) in hyperthyroid patients before and after treatment. MATERIALS AND METHODS A total of five healthy euthyroid patients and five hyperthyroid patients were tested using magnetic resonance elastography (MRE), which involves the induction of shear waves in the thigh muscles using a pneumatic driver at 90 Hz. RESULTS Among the pretreatment hyperthyroid cohort a lower stiffness was found when the muscle was relaxed (2.11 +/- 0.61 kPa) compared the stiffness following treatment of hyperthyroidism (5.52 +/- 1.52 kPa), which was accompanied by an improvement in the contractile function of the VM. Pretreatment muscle stiffness was also less than that of age matched healthy volunteers (4.56 +/- 0.40 kPa). The behavior of the waves was sensitive to the stage of this myopathy and to the amount of free thyroxine (FT4). CONCLUSION The MRE technique provides a new tool to gain new insights into pathophysiology of thyroid associated and other muscle diseases and their response to treatment.