Differentiating primary from secondary hyperparathyroidism in stone patients: the "thiazide challenge".

Differentiating between resorptive hypercalciuria (i.e., primary hyperparathyroidism) and renal leak hypercalciuria (i.e., secondary hyperparathyroidism) in the patient with stones and with hypercalciuria and elevated serum parathyroid hormone is important. Primary hyperparathyroidism necessitates endocrine surgery, while secondary hyperparathyroidism is managed with long-term thiazide diuretics. We present a reliable method for distinguishing between these two conditions: The "thiazide challenge."