Serum phosphorus
In primary hyperparathyroidism, serum phosphorus levels are abnormally low as a result of decreased renal tubular phosphorus reabsorption. This contrasts with secondary hyperparathyroidism, in which serum phosphorus levels are generally elevated because of renal disease.
Alkaline phosphatase
Alkaline phosphatase levels are not elevated in all types of hyperparathyroidism. Kumar and Clark 6 Edition states that alkaline phosphatase levels do not increase in primary hyperparathyroidism but may increase in secondary hyperparathyroidism.