A 10-year analysis of thyrotoxic periodic paralysis in 135 patients: focus on symptomatology and precipitants

Background: A comprehensive analysis has not been performed on patients with thyrotoxic periodic paralysis (TPP) characterized by acute hypokalemia and paralysis in the setting of thyrotoxicosis. Purpose: The aim of this study was to analyze the detailed symptomatology of thyrotoxicosis and precipitating factors for the attack in a large cohort of TPP patients. Patients and methods: A prospective observational study enrolled patients with TPP consecutively over 10 years at an academicmedical center. Clinical features, including signs/symptoms of thyrotoxicosis and precipitating factors, were analyzed. TheWayne's indexwas used to assess the severity of thyrotoxicosis at presentation. Patients who agreed to receive an oral glucose-loading test after recovery were evaluated. Results: Among the 135 TPP patients (male: female, 130:5), 70% of paralytic attacks occurred in the morning, especially during the seasons of summer and fall. Two-thirds of patients did not have a known family or personal history of hyperthyroidism. Only 17% of TPP patientsmanifested overt signs/symptoms of thyrotoxicosis (Wayne's indexO19). Aclear precipitating factor, such as high carbohydrate load, acute upper respiratory tract infection, strenuous exercise, high- salt diet, or the use of steroids or bronchodilators, was identified in only 34% of TPP patients. A glucose load to stimulate insulin secretion induced acute hypokalemia (K+ 2.47G0.6 mmol/ l) with reparalysis in only 18%(10/55) of TPP patients. Conclusions: Most TPP patients have only subtle clinical signs/symptoms of thyrotoxicosis and only a small fraction has clear precipitating factors. In addition to the effects of hyperinsulinemia, other insulinindependent mechanisms may participate in the pathogenesis of TPP.