Hypercalcemia and hypokalemia- is there a link?

Interestingly, we do encounter this combination sometimes and likely has no connection.  This was indeed studied in a 1977 paper in Annals of Internal Medicine. They studied 103 patients with hypercalcemia in a cancer hospital with normal renal function and no history of taking potassium depleting agents. Interestingly, 32% were hypokalemic.  The cause of hypercalcemia is most cases was malignancy followed by primary hyperparathyroidism. Also, as the calcium levels were higher, the frequency of hypokalemia was greatest.

Why does hypercalcemia cause hypokalemia?

Perhaps the calcium delivery increases the na delivery to the distal tubule which in turn results in na-k exchange with loss of potassium. This is what might be postulated based on animal studies and prior human trials.  This above study was only done in the cancer ward and hence might have many other confounders that were not accounted for such as chemotherapy agents that cause low K, diarrhea in setting of infections, chemotherapy and so forth.  While the pathophysiology is plausible, the more likely explanation might be true-true and unrelated.