Thyrotoxicosis presenting with periodic paralysis in a young male: a case report

Periodic paralysis is an uncommon presentation of thyrotoxicosis characterized by acute flaccid paralysis due to hypokalemia. Thyrotoxicosis is often missed as the cause of periodic paralysis due to a lack of overt symptoms. Early recognition and appropriate management can prevent recurrent paralysis and fatal complications, such as cardiac arrhythmias.

We report a case of a 28 years old male who presented with acute-onset flaccid quadriparesis following a carbohydrate-rich meal. Investigations revealed severe hypokalemia (2.1 mmol/L) and thyrotoxicosis. Thyroid scintigraphy was suggestive of Graves' disease. The patient was managed with cautious potassium supplementation, propranolol, and carbimazole, followed by definitive therapy with radioactive iodine ablation.

Thyroid hormone stimulates Na⁺/K⁺-ATPase activity, which causes an intracellular potassium shift, resulting in hypokalemia. Periodic paralysis may be seen in a small percentage of patients with thyrotoxicosis and has a predilection for Asian men. Cautious potassium supplementation is recommended, as rapid supplementation can cause rebound hyperkaliemia. The differential diagnosis includes familial hypokalemic periodic paralysis, Guillain-Barré syndrome, and potassium loss from renal or gastrointestinal causes.

Thyrotoxicosis should be suspected in patients presenting with hypokalemic periodic paralysis, especially in men of Asian descent. Definitive treatment of the underlying thyroid disorder is essential for the prevention of recurrence.