What is your approach to differentiating primary from secondary hyperparathyroidism in recurrent kidney stone formers who also have chronic kidney disease, an elevated PTH, and hypercalcemia?  

You have asked a complicated question. It is certainly possible for both conditions to coexist simultaneously. It would be unusual for primary hyperparathyroidism to cause secondary hyperparathyroidism, although recurrent obstructive uropathy from stones would be a possible etiology. Similarly, seco...