Endocrine Abstracts

Introduction

Thyrotoxic periodic paralysis (TPP) is a rare complication of hyperthyroidism characterized by the sudden onset of hypokalemia and muscle paralysis. This rare but possible clinical presentation of thyrotoxicosis is significantly more predominant in males of asian descent. The mechanisms of hypokalemia are incompletely understood. The prevailing theories include increased Na-K ATPase pump activity and mutations in genes encoding Kir channels in skeletal muscle. Common factors triggering attacks of periodic paralysis include the consumption of carbohydrate-rich foods, strenuous physical activity, high salt/sodium intake, stresses (surgical, infectious, psychological), trauma, and drugs.

Case presentation

We describe a case of a 52 years-old asian-french male who presented to the emergency department with complaints of acute onset of bilateral lower extremity weakness. He also endorsed a history of weight loss, palpitations, heat intolerance and tremors. Physical examination revealed a slightly enlarged thyroid gland. No exophtalmus or skin changes were present. Laboratory assessment showed severe hypokalemia with serum potassium level 1.5 mmol/l, low serum Thyroid Stimulating Hormone (TSH) (< 0.01 mUI/l) and increased both serum free triiodothyronine (27.3 pmol/l) and free thyroxine (63 pmol/l). TSH receptor antibodies were identified (4.2 IU/l). Hence, the patient was diagnosed as having thyrotoxic periodic hypokalemic paralysis associated with Graves’ thyrotoxicosis. Treatment with antithyroid drugs and potassium supplements reversed the symptoms and the episodes of acute muscular weakness did not reappear.

Take-away lesson

TPP is a rare and reversible cause of paralysis. Thus, in cases of acute muscle paralysis, it is important to consider thyrotoxicosis as one of the possible causes, and take measures accordingly. Correction of hypokalemia improves acute presentation, but the patient will remain at risk for paralysis until euthyroid state is achieved.