The condition is uncommon but may be seen more frequently in patients of Japanese or Chinese descent.
Clinical features:
(1) The patient usually has clinical evidence of thyrotoxicosis, although the onset of the periodic muscle weakness may precede the recognition of thyrotoxicosis.
(2) The patient experiences episodes of proximal muscle and trunk weakness.
(3) The serum potassium concentration measured during periods of muscle weakness is decreased.
(4) Factors that cause the serum potassium to fall (administration of insulin, exposure to cold, high carbohydrate load) may precipitate an attack, and oral administration of potassium may be followed by improvement in muscle strength.
(5) Therapy with beta-blockers may prevent attacks.
(6) Unlike a patient with primary hypokalemic periodic paralysis the patient usually does not respond to acetazolamide.
(7) The condition disappears on successful treatment of the underlying condition causing the hyperthyroidism.
