Endocrine Abstracts

Introduction: Hypokalemic periodic paralysis (HPP) belongs to a group of inherited diseases called channelopathies, whose main manifestation include painless muscle paralysis. There are also acquired forms of HPP secondary to hyperthyroidism, called thyrotoxic periodic paralysis (TPP). It’s prevalence is markedly higher in men.

Case Reports: Case 1. 34-year-old Venenzuelan man, without medical history. He consults in the emergency department due to sudden onset of ascending paresthesia and limb weakness, associated to nausea and vomit. He reported intermittent tremor and heat intolerance. Laboratory findings demonstrated severe hypokalemia (1.3mEq/l). He was transferred to ICU for aggressive hypokalemia management, promptly recovering full neurological function after normalizing serum potassium. He didn’t develop arrhythmias. On physical examination, he was clinically hyperthyroid with diffuse goiter. Further laboratory showed a suppressed TSH <0.015, with an elevated fT4 (5.35 ng/dl, normal value (NV) up to 1.79), and T3 2.8 ng/dL (NV up to 1.69). Ultrasound showed chronic thyroiditis. TRAb: 35 IU/l (NV <0.55). Methimazole was started. At follow up, he remains stable, euthyroid and neurologically asymptomatic.Case 2. 32-year-old Chilean man with history of hypertension treated with losartan. He was referred to the emergency department due to limb weakness, with inability to stand up, associated with dyspnea, palpitations, and chest pain. He referred a 20 kg weight loss with preserved appetite, heat intolerance, diaphoresis and progressive weakness. An EKG was performed showing sinus tachycardia with a prolonged PR and QT interval, ST segment depression, and a prominent U wave. Physical examination revealed slight tremor, palpable thyroid without nodules, and hyperdynamic aortic murmur. Initial laboratory tests showed severe hypokalemia (1.6mEq/l). After aggressive correction, patient had full neurological recovery. TSH levels were <0.015, T3 2.95 ng/dL and fT4 4.37 ng/dL and TRAb 8.12 IU/l. Ultrasound showed chronic thyroiditis. Methimazole was started and has remained asymptomatic ever since.

Conclusions: TPP is a rare disease, but it should be considered in a patient with painless muscle weakness and hypokalemia. Aggressive correction is imperative to avoid malignant arrhythmias.