Expert: Christopher Rosch - 1/6/2006

Question
what is the mechanism of controlling calcitonin secration?

Answer
Hello Mohammed,

the concentration of calcium in the blood plasma is constantly monitored. To measure calcium concentration external Ca2+ receptors are expressed in many kinds of cells (e.g. in the kidney or in bone). Ca2+ docking to one or more Ca2+ receptor proteins starts a signal transduction cascade involving G-proteins (similar to the cascades caused by other signals). The strength of the signal depends on the sensitivity of the receptor as well as the number of receptors that bound Ca2+ ions.
In mammals, calcitonin is produced by C cells in the thyroid gland which have external Ca receptors, too. If the amplified signal from the receptor(s) exceeds a certain threshold (I don't know the details), calcitonin is directly released into the bloodstream via vesicles.

http://arbl.cvmbs.colostate.edu/hbooks/pathphys/endocrine/thyroid/casensor.html


"Control of Calcitonin Secretion
The most prominent factor controlling calcitonin secretion is the extracellular concentration of ionized calcium. Elevated blood calcium levels strongly stimulate calcitonin secretion, and secretion is suppressed when calcium concentration falls below normal. A number of other hormones have been shown to stimulate calcitonin release in certain situations, and nervous controls also have been demonstrated."
http://arbl.cvmbs.colostate.edu/hbooks/pathphys/endocrine/thyroid/calcitonin.htm...

Best regards,
Christopher


PS: I'll get back to you later for your other question.