Calcitonin is a 32 amino acid polypeptide with a molecular weight of 3454.93 daltons.
In humans and other mammals, this hormone is produced mainly by the parafollicular cells (also known as C cells) of the thyroid gland, while in birds, reptiles and fish it is produced by the ultimobranchial body.
Calcitonin decreases the blood calcium level when it has risen too high, therefore opposing the effects of parathyroid hormone (PTH), which acts to increase the blood calcium level.
Calcitonin prevents calcium loss from bones, which is particularly important in cases of health conditions that tend to lead to this calcium loss such as pregnancy or being immobilized for a prolonged period due to a fracture or heart attack, for example.
This hormone also prevents the absorption of calcium from the intestine, suppresses the activity of cells called osteoclasts (which dissolve or resorb bone), prevents re-absorption of phosphates and sodium in the kidney and increases magnesium re-absorption in the kidney.
Calcitonin was first isolated and purified in the laboratory in 1962 by Copp and Cheney. The molecule is formed through proteolytic cleavage of a larger prepropeptide, which is coded for by the CALC1 gene. Alternative splicing of this gene gives a 37 amino acid protein product that is distantly related called calcitonin gene-related peptide (CGRP), beta type.
For pharmaceutical manufacture, calcitonin is extracted from the ultimobranchial glands of fish, particularly salmon, as calcitonin from salmon resembles human calcitonin but is more active. Currently, calcitonin is produced either by using recombinant DNA technology or through chemical peptide synthesis. The properties of these synthetic and recombinant preparations are similar in qualitative and quantitative terms.
Reviewed by Sally Robertson