Thyrotoxic periodic paralysis (TPP) is a rare emergency condition that occurs in patients with hyperthyroidism.This condition is more common in Asians, with a documented incidence of approximately 2% in Asian patients with hyperthyroidism and 0.1% to 0.2% in the United States. The most common age group is 20 to 40 years old.Hyperthyroidism is more common in women, but TPP is more common in men.Hypokalemia can be multifactorial,TPP is misleading challenges in the emergency department(ED).

We reported two cases who had sudden onset of paralysis with weakness in the limbs,simultaneous occurrence of hyperthyroidism,and second case report highlights the importance of recognizing,refractory hypokalemia as diagnostic clue to TPP.

First case a 37-year-old man with history of hypokalemia and had dizziness and general weakness for 2 days.His family brought him to our ED for help. PE showed clear consciousness, supple neck, clear breath sound, soft abdomen without tenderness and freely-movable limbs.Lab data:Ca(Calcium):9.5 mg/dL Na(Sodium):140 mmol/L ;K(Potassium):2.0 mmol/L;FT4:5.88 ng/dL;TSH :＜0.005 uIU/mL.The EKG:Sinus rhythm, CxR : no active lung lesion. He was diagnosed to TPP with hypokalemia.Rx: ATD with IV fluid supply with KCL . Second case a 32-year-old female with asthma was in her usual health status until 2 days ago when cough and rhinorrhea developed,and general limbs weakness for one day, referral to our ED,PE:BP:170/118 ; Muscle power:lower limbs:2-3.was noted. Lab showed K:＜1.5 mmol/L,AST:39U/L; LDH:232U/LEKG：Sinus rhythm, QT prolongation.CxR:clear lung field..After 6 hours FT4:1.72 ng/dL,TSH:5.40 uIU/mL Under the impression of hypokalemia with suspected TPP,admitted to MICU,after the Lab data:FT4:1.49 ng/dL,TSH:0.762 uIU/mL,treatment with ATD & Inderal treatment,she was followed our OPD with potassium supplement,but hypopotassium around 2.2~2.8 mmol/L,in favior of refractory hypokalemia TPP.

TPP is a rare,but life-threatening complication of hyperthyroidism that often goes under recognized.In front of hypokalemic paralysis with hyperthyroidism, the condition is more likely to be triggered by high-sugar foods, alcohol, and strenuous exercise, which should be avoided .Long-term maintenance of euthyroid status is the keystone in preventing TPP recurrence.