TLDR: Calcitonin is a hormone that helps regulate calcium levels in the body, produced by the thyroid gland. It works by reducing blood calcium levels and opposing the effects of another hormone called parathyroid hormone.
Calcitonin is a hormone made up of 32 amino acids that is secreted by the parafollicular cells (also known as C cells) of the thyroid gland. It plays a role in calcium metabolism, but its importance in humans is not as well established as in other animals. Calcitonin helps to lower blood calcium levels by inhibiting the activity of osteoclasts, which are cells that break down bone. It also inhibits the reabsorption of calcium and phosphate in the kidneys, allowing them to be excreted in the urine. However, the effects of calcitonin on calcium regulation in humans are not as significant as those of other hormones like parathyroid hormone.
Calcitonin is produced through the cleavage of a larger prepropeptide, which is the product of the CALC1 gene. It is regulated by factors such as an increase in blood calcium levels and the presence of certain hormones like gastrin and pentagastrin.
The main function of calcitonin is to help maintain calcium homeostasis in the body. It does this by inhibiting bone resorption and promoting bone formation. It also helps to prevent postprandial hypercalcemia, which is an increase in blood calcium levels after eating. Additionally, calcitonin has been found to have effects on food intake, feeding behavior, and the regulation of appetite.
Calcitonin acts on target cells through a receptor called the calcitonin receptor, which is a G protein-coupled receptor. When calcitonin binds to this receptor, it stimulates the production of cyclic AMP (cAMP) in the target cells. The receptor is primarily found on osteoclasts, but it is also present in other cells such as those in the kidneys and brain.
Calcitonin was first discovered in 1962 and has since been used in the diagnosis and treatment of various conditions. It can be used as a tumor marker for medullary thyroid cancer, as elevated levels of calcitonin may indicate the presence of this type of cancer. Calcitonin has also been used therapeutically for the treatment of conditions such as hypercalcemia and osteoporosis. It can be administered through injections or nasal sprays.
In conclusion, calcitonin is a hormone that helps regulate calcium levels in the body. It works by reducing blood calcium levels and opposing the effects of parathyroid hormone. Calcitonin is produced by the thyroid gland and acts on target cells through a receptor called the calcitonin receptor. It has various functions in calcium metabolism and has been used in the diagnosis and treatment of certain conditions.