Diagnostic algorithm for the workup of hypercalcemia. The diagnostic workup for patients presenting with hypercalcemia rests on the measurement of parathyroid hormone (PTH) to divide patients into those with elevated versus suppressed PTH values. Urine calcium-creatinine ratio should be derived from a 24-hour urine collection.44 Of note, at calcium-creatinine ratio cutoff value of 0.0115, sensitivity for correct classification of familial hypocalciuric hypercalcemia (FHH) was 0.80 and specificity was 0.88, thus misclassifying 20% of patients with FHH and 12% of primary hyperparathyroid patients.45 Thus, further testing and family history should be used to conclusively diagnose FHH. Abbreviations: CaSR, calcium-sensing receptor; iPTH, intact PTH; PTHrP, PTH-related peptide.

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