ODP614 Two cases of Graves Disease Associated Hypokalemic Periodic Paralysis

INTRODUCTION: Periodic paralysis (PP) is a rare neuromuscular disorder due to a defect in ion channels in muscle, characterized by episodes of painless muscle weakness or paralysis, which may be precipitated by heavy exercise or high-carbohydrate meals. Hypokalemic PP (HPP) is most common of the periodic paralyses, however is still very rare, with an estimated prevalence of 1 in 100,000. An acquired form of hypokalemic PP can be seen in thyrotoxicosis of any cause. We present 2 cases of HPP due to thyrotoxicosis. CASE 1: 27 year old Asian male presented to the ED due to sudden onset of acute weakness/near paralysis in lower extremities, with weakness of bilateral upper extremities. He was found to be hypokalemic with a potassium of 2.0 mmol/L (3.5-5.1). At the same time, he was also found to be hyperthyroid with a suppressed TSH of 0.03 uIU/Ml (0.35-5.5) and a free T4 2.2 ng/mL (0.5-1.3), Total T3 225 ng/Dl (70-204), Free T3 5.9 pg/mL (1.5-4.1). TSI antibodies elevated at 1.39 IU/L (<0.10). He was started on potassium supplements and methimazole. At a 3-month follow-up, patient reported no further episodes of weakness or paralysis. CASE 2: 23 year old White male presented to ED with severe muscle weakness and was found to have hypokalemia of 2 mmol/L (3.5-5.1). On further labs, TSH was undetectable at less than 0.01 uIU/mL (0.35-4.94), Free T4 2.81 ng/dL (0.61-1.82), Total T3 of 451 ng/dL(48-178), TSI antibodies were positive at 178%(</=122%). Nuclear uptake scan confirmed Graves’ disease with radioactive iodine uptake of 58.1% at 4 hours and 70% at 24 hours with homogenous uptake in the entire gland and no evidence of hot or cold nodules. He was started on methimazole and propranolol for tachycardia and palpitations and potassium supplements. Muscle weakness resolved on treatment methimazole. DISCUSSION AND CONCLUSION: We present two cases of HPP likely caused by Graves’ disease. Both patients presented with hypokalemia and further workup revealed underlying thyrotoxicosis. The exact mechanism behind HPP due to thyrotoxicosis is not well understood. It is proposed that excess thyroid hormone may predispose to paralytic episodes by increasing the susceptibility to the hypokalemic action of epinephrine or insulin. This condition has been most widely reported in Asian populations, in which the incidence is approximately 2% in contrast to non-asian population with incidence of 0.1 to 0.2%, and is more common in men. Treatment of thyrotoxicosis with restoration and maintenance of euthyroid state ceases attacks. To summarize, few case series report the association of HPP with Graves’ disease. These patients usually present acutely with severe muscle weakness or paralysis. In conclusion, in diagnosis of HPP, possibility of thyrotoxicosis should be considered, especially in the absence of family history of PP. Presentation: No date and time listed