PERIODIC paralysis is a rare complication of hyperthyroidism except in Japan1-3 and countries having many people of Japanese ancestry.4 Between 2% and 8% of hyperthyroidal Japanese suffer from periodic paralysis,3-5 and in adult males the incidence may be as high as 33%.3
Thyrotoxic periodic paralysis (TPP) resembles familial periodic paralysis (FPP) in clinical features, accentuation by exercise or carbohydrate loads, and hypokalemia.2-5 Intramuscular vacuoles, which are a notable feature of the histopathology in FPP,6 have also been found in TPP during paresis.3 This finding has recently been confirmed in an electron microscopic study.7
There are, on the other hand, important differences between TPP and FPP. The paralytic episodes in TPP generally parallel the hyperthyroidal state, and can be greatly alleviated or cured by appropriate thyroid treatment,1,3-5 while attacks of FPP are associated with a falling metabolic rate.1,8 TPP also
Norris FH, Panner BJ, Stormont JM. Thyrotoxic Periodic Paralysis: Metabolic and Ultrastructural Studies. Arch Neurol. 1968;19(1):88–98. doi:10.1001/archneur.1968.00480010106009
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