Calcitonin is produced by the C-cells located in the thyroid gland and its main function is to decrease plasma calcium. This is done primarily through the activation of osteoblasts, which take calcium in the blood and store it in bone.

When blood calcium levels are low, parathyroid hormone is released to increase calcium reabsorption of the kidneys and to stimulate osteoclasts, which are responsible for bone resorption. These processes serve to increase blood calcium levels.

Parathyroid hormone is an antagonist to calcitonin, which is released from the thryoid gland and increases blood calcium levels.

In accordance with negative feedback and homeostasis, low blood calcium levels will cause the body to release a hormone in order to raise calcium levels. Parathyroid hormone is a hormone that acts to raise blood calcium levels by stimulating osteoclast activity, releasing stored calcium from bone into the blood. The parathyroid gland would be most active during low blood calcium in order to initiate this effect.

The thyroid gland is involved in raising blood calcium levels (calcitonin) and mediating metabolism (T3 and T4). The pancreas moderates blood glucose levels (insulin and glucagon). The pituitary gland is associated with several processes, including stimulation of other endocrine glands, but is not linked to parathyroid activity. The thymus is located superior to the heart and is the location of maturation for T-lymphocytes; it also secretes certain hormones that affect immune system maintenance and development.