The calcitonine is a Hormone (peptide of 32 amino-acids) hypocalcémiante (decreases the rate of Calcium in blood) and hypophosphatémiante (the rate of Phosphate in blood decreases) which takes part in the Métabolisme of the Calcium and of the Phosphore. Specifically, it reduces the calcemy (blood rate of Calcium) in three manners:

• Principalement, it activates the Ostéoblaste S, which increases the storage of calcium in the bones
• It decreases the absorption of calcium by the Duodénum by decreasing the activity of the Vitamine D
• It increases the excretion of calcium by the Rein S.

The major part of the calcitonine of the human body is produced in the Cellules C (cells parafolliculaires) of the thyroid gland.

Calcitonine is used in the treatment of the Ostéoporose postménopausale.