Abstract: A method for predicting reactivity to parathyroid hormone by determining the genotype with respect to polymorphism in the parathyroid hormone receptor gene. The results obtained by the analysis of genetic polymophism are useful for predicting the tendency for a hemodialyzed patient to develop severe secondary hyperparathyroidism, or for predicting the tendency for a human individual to develop severe primary hyperparathyroidism. Also, this method is useful for predicting the therapeutic effects by predicting reactivity to parathyroid hormone in a patient who is being treated for regressive osteoporosis by administration of parathyroid hormone.