Hypokalemic periodic paralysis associated with hypophosphatemia in a patient with hyperinsulinemia

A 34-year-old man was admitted to the hospital because of acute quadriplegia. On admission, serum potassium was 2.1 mEq/L and serum inorganic phosphate was 1.4 mg/dL. Thyroid function was normal. Serum levels of aldosterone, cortisol, and intact parathyroid hormone were normal. Fasting plasma glucose was 109 mg/dL, and fasting serum insulin was 25.0 U/mL. Shortly after intravenous supplementation of potassium, muscle strength was normalized. Oral glucose tolerance test revealed impaired glucose tolerance and hyperresponse of insulin. During the oral glucose tolerance test, serum potassium and phosphate decreased significantly. These findings suggest that hyperinsulinemia and insulin-induced transmembrane shift of extracellular potassium and phosphate may have been involved in the abnormalities of serum electrolytes and development of hypokalemic periodic paralysis in the present patient.