Periodic hypokalemic paralysis can be of genetic origin or secondary to other causes of hypokalaemia. The thyreotoxic hypokalemic periodic paralysis (THPP) usually occurs among asian subjects. It is a diagnostic and therapeutic emergency which may lead to life-threatening complications due to hypokalaemia and muscle weakness. The potassium supplementation is followed by a complete recovery after a few hours. We underlined the interest of thyroid assays in patients having an acute muscular paralysis associated with hypokalaemia.