Acute onset of hypokalemia and muscular weakness in four hyperthyroid cats.

Sudden onset of muscular weakness and ventroflexion of the neck were identified in 4 hyperthyroid cats. In each cat, the onset of clinical signs was associated with an acute decrease in serum potassium concentration. The cause for hypokalemia was undetermined, but could have resulted from deficits in total body potassium content or shifts of potassium from the extracellular space into the intracellular space. The 4 cats responded to administration of potassium. Hyperthyroid cats may be prone to disturbances in potassium homeostasis. Clinicians should be aware of potential changes in potassium homeostasis during the treatment of cats with hyperthyroidism.