The study investigates the importance of determining the intact parathormone in the evaluation of parathyroid gland function in different conditions of change in their function and the alteration of parathormone metabolism: primary and secondary hyperparathyroidism, hypoparathyroidism and hyperthyroidism. The role and place of intact parathormone determination in routine diagnostic schemes of calcium homeostasis disorders was reviewed by the simultaneous determination of the indicators of calcium and bone metabolism and other calcium homeostasis hormone regulators, as well as the C- and N-terminal parathormone fragments and by establishing their mutual links with the values of the intact parathormone.