Another adrenal cortex deficiency disease is hyporeninemic hypoaldosteronism. Since this condition is usually due to a deficiency of renin, the disorder is a secondary rather than a primary defect in aldosterone secretion. The characteristic laboratory feature is hyperkalemia, and the condition is usually discovered when a patient is found to have hyperkalemia not due to any other cause. The serum sodium level is normal or mildly decreased. There may be a mild metabolic acidosis. If dietary sodium is restricted, renal salt wasting develops, since deficiency of aldosterone makes it difficult to conserve sodium. Hyperkalemia is not diagnostic of hyporeninemic hypoaldosteronism since it may be found in Addison’s disease, salt-wasting congenital adrenal hyperplasia, renal failure, and other conditions listed in the chapter on serum electrolytes.