Thyrotoxic Periodic Paralysis Associated With Graves' Disease

Abstract

Introduction: Thyrotoxic periodic paralysis is an uncommon, life-threatening complication of hyperthyroidism characterized by acute flaccid paralysis and severe hypokalemia due to an intracellular shift of potassium.

Case Report: A 20-year-old male of Southeast Asian descent presented with sudden-onset, symmetrical flaccid quadriparesis upon waking. Neurological examination revealed proximal-predominant muscle weakness and diminished deep tendon reflexes with preserved sensory function. Biochemical evaluation confirmed severe hypokalemia (2.13 mmol/L) accompanied by primary hyperthyroidism, with a suppressed thyroid-stimulating hormone level (<0.05 µIU/L) and elevated free thyroxine (66.7 pmol/L). Electrocardiography demonstrated ST-segment depression and QT-interval prolongation, and thyroid ultrasonography suggested diffuse edema consistent with Graves' disease.

Discussion: Cautious intravenous and oral potassium replacement, coupled with oral propranolol and propylthiouracil, led to rapid normalization of potassium levels and complete motor recovery within 24 hours without rebound hyperkalemia.  

Conclusion: This case emphasizes the necessity of screening for underlying thyroid dysfunction in young adults presenting with unexplained hypokalemia paralysis to prevent fatal cardiopulmonary complications.