 The effects of OFC on bone are largely dependent on the duration of the disease and the level of parathyroid hormone ( PTH ) produced . PTH is responsible for maintaining a homeostatic calcium concentration in the blood . It activates the parathyroid @-@ hormone related protein receptor located on osteoblasts and osteocytes , both of which are responsible for the building and calcification of bone . Abnormalities affecting the parathyroid glands cause a surplus of PTH , which , in turn , increases the activity and frequency of osteoblasts and osteocytes . Increased PTH levels trigger the release of stored calcium through the dissolution of old bone , as well as the conservation of serum calcium through a cessation in the production of new bone . 
