Answer:
A) An increase in calcitonin produced by the thyroid gland.
Explanation:
Calcitonin is also referred as thyrocalcitonin (TCT). It is a protein hormone and is secreted by the parafollicular cells or C-cells of thyroid gland. It is secreted in response to high blood calcium levels. It is also know as hypocalcemic hormone as it helps in reducing the blood calcium levels to normal.
Calcitonin once released helps in reducing the blood calcium levels to normal by:
1.Calcitonin inhibits osteoclasts, which dissolve the bone matrix and cause demineralization moving the bone calcium to blood.
2. Calcitonin also inhibits the absorption of calcium in the gut.
3. It increases the excretion calcium.
Generally the calcium homeostasis is regulated by three hormones: TCT, parathyroid hormone and calcitriol. Parathyroid hormone and calcitriol are produced when there is low calcium in blood plasma whereas calcitonin is produced when there is high calcium in blood plasma.
