[Thyrotoxic periodic paralysis. A report of 2 cases]

Thyrotoxic hypokalemic periodic paralysis is characterized by recurrent episodes of motor weakness of variable intensity associated with thyroid overactivity. It is usually associated with low plasma potassium levels and is often precipitated by physical activity or ingestion of carbohydrates.

We describe two men, aged 33 and 50, who complained of several episodes of muscular paralysis in the context of previously undiagnozed hyperthyroidism and associated with low plasma potassium levels. There were clearly raised levels of T3, T4 and free T4 and TSH was depressed due to hyperactive diffuse goitre. In one patient the precipitating factor was known to have been a large intake of carbohydrates and intense physical exercise. Antithyroid treatment, and the resulting correction of hyperthyroid function, prevented any further episodes of muscular weakness in both patients.

Thyrotoxic periodic paralysis should be considered in the differential diagnosis of all acute episodes of motor paralysis in young patients. Determination of the plasma levels of potassium and thyroid hormones helps diagnosis. Early diagnosis is important so as to be able to establish antithyroid treatment and avoid further episodes of weakness.