Final answer:
Calcitonin is secreted by the thyroid gland and its main target tissue is the bones. It inhibits osteoclast activity and promotes calcium absorption and deposition in the bones to maintain calcium homeostasis.
Step-by-step explanation:
The hormone calcitonin is secreted by the thyroid gland. It is produced by the parafollicular cells, also called C cells, that are present in the tissue between distinct follicles in the thyroid gland.
Calcitonin is released in response to a rise in blood calcium levels. Its main target tissue is the bones, where it inhibits the activity of osteoclasts and promotes calcium absorption and deposition in the bone.
This hormone works in conjunction with parathyroid hormone (PTH) to maintain calcium homeostasis in the body.