Thyrotoxic periodic paralysis in caucasians. Report of 8 cases

Periodic paralysis is a well known complication of thytotoxicosis in Chinese and Japanese patients, but has been considered extremely rare in caucasians.

Between 1991 and 1996, we admitted 8 caucasian patients to our Hospital due to thyrotoxic periodic paralysis. We retrospectively analysed their clinical manifestations.

All the patients were males. Their attacks started at night or early after awakening, frequently triggered by a high carbohydrate diet and physical exertion. Myalgias and flaccid weakness predominated over proximal leg muscles, sparing bulbar and respiratory musculature. Reflexes were brisk at the onset of the attack and reduced or absent during the course of the episode. Prior to diagnosis patients presented 1-5 attacks of thyrotoxic periodic paralysis each lasting 1-96 hours. Hypokalemia was documented in 6 patients. The episodes of periodic paralysis led to the diagnosis of a previously unsuspected thyrotoxicosis in 6 patients. In the other 2 patients the diagnosis of the thyroid dysfunction preceded the periodic paralysis. Attacks resolved after treatment of the hyperthyroid state.

Thyrotoxic periodic paralysis is an under-diagnosed but probably frequent complication of hyperthyroidism in caucasians. Early recognition of the attacks is essential to investigate and treat the underlying thyroid dysfucntion whose symptoms are usually mild. The episodes of periodic paralysis resolve with the correction of the hyperthyroidism.