Acute exertional rhabdomyolysis in hypothyroidism: the result of a reversible defect in glycogenolysis?

A 28-year-old man on thyroid hormone replacement following treatment with radioactive iodine for Graves' disease developed an episode of acute exertional rhabdomyolysis. He was found to be hypothyroid and had no rise in serum lactic acid following an ischemic exercise test. With additional thyroid replacement, his ischemic exercise test normalized and his muscle symptoms resolved. This observation suggests that rhabdomyolysis in hypothyroidism may be due to a reversible defect in glycogenolysis and that hypothyroidism should be excluded in patients with rhabdomyolysis and/or myoglobinuria.