Generally, for hypercalcemia with normal PTH values, various differential diagnoses must be taken into consideration, including osteolysis for bone metastases of cancer, granulomatous diseases, medication with influence on calcium excretion or familial hypocalciuric hypercalcemia (FHH, a rare genetic disease which leads to a reduced sensitivity of the parathyroid CaSR to elevated calcium levels) [28–30]. Here, CASR is linked to hereditary disease.