Rhabdomyolysis Induced by Nonstrenuous Exercise in a Patient with Graves’ Disease

Hyperthyroidism can result in several musculoskeletal conditions such as thyrotoxic periodic paralysis, thyrotoxic myopathy, and thyroid ophthalmopathy. Rhabdomyolysis has been rarely reported to be associated with hyperthyroidism. We describe a 33-year-old man who presented with bilateral thigh pain and dark brown urine after regular squatting. He had a past medical history of hyperthyroidism but stopped taking it 2 months prior to admission. He was found to have rhabdomyolysis, myoglobinuria, and thyrotoxicosis. Presence of thyroid-stimulating immunoglobulins (TSI) and high radioiodine uptake confirmed a diagnosis of Graves' disease. He received aggressive fluid resuscitation and sodium bicarbonate intravenously along with monitoring fluid and electrolyte. Methimazole was also resumed. The patient responded to treatment and rhabdomyolysis gradually resolved. Therefore, nonstrenuous exercise can potentially induce rhabdomyolysis in patients with hyperthyroidism. Although hyperthyroidism is not widely recognized as a cause of rhabdomyolysis, it should be considered in the differential diagnosis of rhabdomyolysis. 1. Introduction Rhabdomyolysis is characterized by muscle necrosis resulting in the release of muscle cell content into the circulation. This condition has been occasionally associated with strenuous exercise, hyperthermia, certain infections, and metabolic abnormalities such as diabetic coma, severe electrolyte disturbances, and hypothyroidism [1]. In the English literature, hyperthyroidism has been rarely reported to be associated with rhabdomyolysis [1–6]. We have described the case with hyperthyroidism who developed rhabdomyolysis after nonstrenuous exercise. 2. Case Presentation A 33-year-old male presented with bilateral thigh pain after regular squatting. The patient often squatted for exercise and never developed rhabdomyolysis. On the following day, the patient developed severe bilateral pain and stiffness in both thighs. He took Tylenol for pain and denied using any steroid or illicit drugs. He noticed dark brown-colored urine which urged him to come to the hospital. There was no history of fever, cough, sore throat, headache, blurred vision, palpitations, diarrhea, or abdominal pain. The patient also had a past medical history of hyperthyroidism and was taking methimazole which he stopped 2 months prior to admission. On physical examination, the patient was alert and oriented in no acute distress. His blood pressure was 137/77？mmHg and pulse was 100 beats per minute, and he was afebrile. His eyes showed no lid lag or exophthalmos. An