Also Known As: Calcitonin, Thyrocalcitonin
Calcitonin (also known as thyrocalcitonin) is a 32-amino acid linear polypeptidehormone that is produced in humans primarily by the parafollicular cells (also known as C-cells) of the thyroid, and in many other animals in the ultimobranchial body.It acts to reduce blood calcium (Ca2+), opposing the effects of parathyroid hormone(PTH). Calcitonin has been found in fish, reptiles, birds, and mammals. Its importance in humans has not been as well established as its importance in other animals, as its function is usually not significant in the regulation of normal calcium homeostasis. It belongs to calcitonin-like protein family.
Calcitonin is formed by the proteolytic cleavage of a larger prepropeptide, which is the product of the CALC1 gene (CALCA). The CALC1 gene belongs to a superfamily of related protein hormone precursors including islet amyloid precursor protein, calcitonin gene-related peptide, and the precursor of adrenomedullin.
Secretion of calcitonin is stimulated by:
- an increase in serum [Ca2+]
- gastrin and pentagastrin.
The hormone participates in calcium (Ca2+) and phosphorus metabolism. In many ways, calcitonin counteracts parathyroid hormone (PTH).
More specifically, calcitonin lowers blood Ca2+ levels in three ways:
- Inhibits Ca2+ absorption by the intestines
- Inhibits osteoclast activity in bones
- Inhibits renal tubular cell reabsorption of Ca2+ allowing it to be excreted in the urine
However, effects of calcitonin that mirror those of PTH include the following:
In its skeleton-preserving actions, calcitonin protects against calcium loss from skeleton during periods of calcium mobilization, such as pregnancy and, especially,lactation.
Other effects are in preventing postprandial hypercalcemia resulting from absorption of Ca2+. Also, calcitonin inhibits food intake in rats and monkeys, and may haveCNS action involving the regulation of feeding and appetite.
The calcitonin receptor, found on osteoclasts, and in kidney and regions of the brain, is a G protein-coupled receptor, which is coupled by Gs to adenylate cyclaseand thereby to the generation of cAMP in target cells. It may also affect the ovaries in women and the testes in men.
- Postmenopausal osteoporosis
- Paget's disease
- Bone metastases
- Phantom limb pain
It has been investigated as a possible non-operative treatment for spinal stenosis.
The following information is from the UK Electronic Medicines Compendium