CASR and familial hypocalciuric hypercalcemia: The EC<sub>50</sub> study also demonstrated the correctable effect of calcimimetics on the function of the <i>CASR I554N</i> mutation.<h4>Conclusion</h4>This novel <i>CASR I554N</i> mutation causing FHH attenuates CASR stability, its binding affinity with Ca<sup>2+</sup>, and the response to eCa<sup>2+</sup> corrected by therapeutic calcimimetics.