Calcitonin, also called thyrocalcitonin because it is produced by the C cells of the thyroid, which are not part of the follicle wall and pour calcitonin into the capillaries, is another regulatory hormone of calcium metabolism.

Calcitonin is also a peptide and is synthesized in the form of prepro-calcitonin, it has opposite effects to those of parathormone and when calcium exceeds a certain level besides inhibiting the secretion of parathormone, it increases the secretion of calcitonin. The receptor increases the levels of cyclic AMP and PLC. Calcitonin has a primary role on osteoclasts that have a specific receptor, in the presence of calcitonin the activity of osteoclasts is inhibited. 

In the kidney it determines the lowering of calcium and phosphate reabsorption. However it is believed that parathormone is sufficient to determine calcium levels, while calcitonin seems to have a much more marginal role. 

Molecular Formula  C₁₄₅H₂₄₀N₄₂O₄₆S₂

Molecular Weight  3371.8 g/mol

Synonyms

• Calcitrin
• Thyrocalcitonins
• TCA
• TCT
• Thyrocalcitonin
• FT-0688039