PTH and cancer: It also helps to regulate blood calcium by reducing the amount of calcium released from the bones by working in the opposite way to parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D. Calcitonin has been used clinically for treatment of hypercalcemia and osteoporosis and although it is predominantly used for postmenopausal osteoporosis, it can also be used for treating Paget’s disease, osteogenesis imperfecta, bone metastases, and malignancy-associated hypercalcemia.