In a certain condition (osteopetrosis), too much bone is deposited. What cells do you think are affected here and how are they affected to create this condition? Why is supplemental (pharmaceutical) calcitonin sometimes prescribed to patients with osteoporosis? Which is more detrimental to blood calcium homeostasis – loss of the parathyroid gland or thyroid gland (assume each gland is removed by itself, leaving the other)? How would a tumor of the parathyroid gland affect the skeleton? (Tumor would result in excess PTH release.) Why, in terms of the skeleton, is exercise recommended at all life stages?