Calcitonin is a hormone produced by the thyroid gland that plays a crucial role in regulating calcium levels in the body. It is primarily responsible for decreasing blood calcium concentrations by inhibiting the activity of osteoclasts – cells involved in the breakdown of bone tissue.
Structurally, calcitonin is a peptide hormone composed of 32 amino acids. It is synthesized in specialized cells known as parafollicular or C-cells located within the thyroid gland. Upon release, calcitonin acts on various target tissues, including bone, kidneys, and intestines.
In bones, calcitonin helps maintain calcium homeostasis by inhibiting osteoclast activity, which reduces the resorption of bone tissue. This action ultimately decreases the release of calcium from bones into the bloodstream. Consequently, calcitonin promotes bone formation and mineralization.
Calcitonin also influences kidney function by promoting the excretion of calcium through urine. By inhibiting tubular reabsorption of calcium, it reduces the amount of calcium that is absorbed back into the bloodstream from the filtrate.
Additionally, calcitonin may exert inhibitory effects on intestinal calcium absorption. By reducing the uptake of calcium from the diet, it contributes to lowering blood calcium levels.
The regulation of calcium levels is essential for various physiological processes, such as maintaining bone strength, facilitating muscle contractions, enabling nerve transmission, and assisting blood clotting. Therefore, calcitonin plays a vital role in maintaining calcium balance and preventing conditions associated with excessive calcium levels, such as hypercalcemia.
