A method of assessing the efficacy of a calcimimetic drug to treat hyperparathyroidism in a subject may include determining which alleles for a calcium-sensitive receptor (CaSR) gene the subject carries; and concluding that the calcimimetic drug will have a first or highest efficacy if the subject has a .sup.990Gly-.sup.990Gly genotype, a second or intermediate efficacy if the subject has a .sup.990Gly-.sup.990Arg genotype, or a third or lowest efficacy if the subject has a .sup.990Arg-.sup.990Arg genotype. In one embodiment, the calcimimetic drug may be cinacalcet or any pharmaceutically acceptable salt thereof.