Insulin-induced severe thyrotoxic periodic paralysis: A case report

Thyrotoxic periodic paralysis (TPP) is an endocrine emergency caused by thyrotoxicosis, manifesting mainly as periodic myasthenia and hypokalemia, and posing a serious threat to the patient's health. Fatigue, strenuous exercise, alcohol abuse, high carbohydrate intake and insulin injections are common triggers of paralysis. This article reports a case of severe TPP induced by insulin injection, elucidates the characteristics and pathogenesis of the disease, analyses the risk factors for triggering TPP, and hopefully provides more clinical data for TPP patients.

A 38-year-old Asian man presented to the emergency department with a one-week history of limb weakness and worsening half-day. His medical history included poorly controlled type 2 diabetes and he had been switched to Aspart50 a week earlier. He was alert and oriented with upper extremity strength grade 3 and lower extremity strength grade 1. Emergency department tests showed hypokalemia of 1.6 mmol/L. The paramedics administered 1.5 g of potassium intravenously, followed by 4.0 g orally. Weakness in the arms and legs improved. He was referred to endocrinology where he was diagnosed with Graves' disease, with suboptimal control and insulin injections possibly causing TPP. We stopped his insulin and he was discharged with a potassium level of 4.0 mmol/L.

Insulin is a trigger for TPP and should be avoided in patients with hyperthyroidism. Early recognition and treatment of TPP is crucial, especially in patients presenting with hypokalemic periodic paralysis.