Silent thyrotoxicosis unveiled by sudden paralysis: a case report of thyrotoxic hypokalemic periodic paralysis

Abstract Background Thyrotoxic hypokalemic periodic paralysis is a rare but potentially life-threatening complication of hyperthyroidism, characterized by sudden episodes of reversible muscle weakness due to an intracellular shift of potassium. Although predominantly affecting young Asian males, it often represents the initial presentation of previously undiagnosed thyrotoxicosis. The case of a young Chinese male presenting with thyrotoxic hypokalemic periodic paralysis as the initial manifestation of Graves’ disease is reported. Case presentation A 28-year-old Chinese male patient presented with acute flaccid tetraparesis and sinus tachycardia. Neurological examination revealed reduced muscle strength, weak reflexes, and negative pyramidal signs. Laboratory investigations showed severe hypokalemia (1.9 mmol/L), suppressed thyroid-stimulating hormone (< 0.01 mU/L), and significantly elevated thyroid hormone levels. The patient received potassium supplementation and antithyroid treatment with thiamazole, sodium perchlorate, and propranolol. Within 24 h, potassium levels normalized and motor function nearly fully recovered. Thyroid sonography revealed increased vascularization, and positive TSH receptor antibodies confirmed the diagnosis of Graves’ disease. The patient remains under regular follow-up with ongoing antithyroid therapy. Conclusions This case highlights the importance of early recognition of thyrotoxic hypokalemic periodic paralysis, particularly in young men of Asian descent. It may represent the first and most dramatic presentation of previously undiagnosed Graves’ disease. Prompt diagnosis and appropriate management can lead to rapid and complete recovery, underscoring the time-dependent nature of treatment success.