Endocrine Abstracts

A rare complication of thyrotoxicosis among Asians is Thyrotoxic Periodic Paralysis (TPP), with an incidence of approximately 2% in patients with thyrotoxicosis from any cause. TPP is characterized by sudden onset of hypokalemia and muscle paralysis. Hypokalemia in TPP results from an intracellular shift of potassium induced by the thyroid hormone sensitization of Na⁺ /K⁺ −ATPase rather than depletion of total body potassium. Treatment of TPP includes correcting the underlying hyperthyroid state, prevention of potassium shift by using non-selective beta-blockade, and replacing potassium. TPP is curable once a euthyroid state is achieved. We describe here a rare case of TPP in a young Chinese man who presented with sudden bilateral lower limb weakness. A 23-year-old gentleman of Chinese origin, presented to the outpatient department with complain of bilateral lower limb weakness for one day. Motor examination revealed normal bulk and reflexes bilaterally but power was 2/5 in both the lower limbs. His initial electrolytes showed severe hypokalemia of 1.3 mmol/l (Range: 3.5-5.1 mmol/l). Hypokalemia was rapidly corrected with IV potassium. His symptoms subsequently improved and patient was discharged. At discharge his potassium level was 4.1 mmol/l. Follow up was advised but patient was lost to follow up. Three weeks after the initial presentation, patient again presented to the emergency department with complaints of sudden onset of bilateral lower limb weakness. Motor examination of the lower limb revealed decreased tone and power was 1/5 bilaterally. No goiter, lid lag and lid retraction noted. Rest of the systemic examination was unremarkable. Laboratory findings were significant for a potassium of 1.3 mmol/l). Potassium (K) was replaced intravenously (IV) and when rechecked, the potassium level was 5.2 mmol/l. Patient lower limb weakness also improved clinically. Endocrinology was consulted as laboratory workup revealed a suppressed TSH (<0.010 uIU/ml). We advised checking FT3, FT4 and thyroid receptor antibodies (TRAB). FT4 was markedly elevated at 4.24 ng/dl (Range: 0.89-1.76 ng/dl) and TRAB was positive 8.85 IU/l (Range : 0-1.75 IU/l). Endocrine team recommended initiating anti-thyroid medication, Neomarcazole 15 mg two times a day. He was discharged as soon as K levels normalized. Potassium on discharge was 4.9 mmol/l. It is important to consider TPP as a differential in a patient presenting with low potassium levels and neurological symptoms as management initially with propranolol and of the underlying thyrotoxicosis is essential in definitive treatment of the recurrent periodic paralysis.