Calcitonin-a Hormone from the Parathyroid which Lowers the Calcium-level of the Blood

CONTROL of the calcium-level in blood is the primary function of the parathyroids. McLean¹ has suggested that this is accomplished through a `feedback' mechanism, by which a low level of calcium in the blood stimulates the glands to produce parathyroid hormone which in turn mobilizes calcium from bone and restores the normal level. High levels of calcium are assumed to suppress production of this hormone.