Consult rounds: Electrolyte abnormalities associated with Primary hyperparathyroidism

Classically, we are notified to see a patient with hypercalcemia and one of the diagnosis that is made is primary hyperparathyroidism (PHPT). Due to the elevated PTH, what other electrolytes can go out of order?

1.       Hypophosphatemia:  Elevated PTH levels tend to lead to phosphate wasting in the urine.  Proximal tubular absorption of phosphorus( Na –Phos co transporter)  is blocked leading to renal wasting.

2.       Hypomagnesemia: This one is interesting as hypercalcemia would lead to decrease magnesium absorption via Ca-Sensing receptor in the TAL but PTH would increase magnesium absorption.  But net effect usually is “ hypercalcemia” wins leading to mg wasting as well. This in turn might lead to hypokalemia as well.

3.       Metabolic acidosis: Elevated PTH levels lead to decrease proximal bicarbonate absorption and leading to mild metabolic acidosis. This is usually seen when you have AKI as well compounding this problem.