Expert: Christopher Rosch - 1/5/2006

Question
CALCITONIN and blood calcium mechanism is a negative feedback or a possetive feedback?
(please right me a refrance too it is better to be a link )

Answer
Hello Mohammed,

Calcitonin, a peptide hormone released by the thyroid gland, controls the Ca2+ level in blood. An increased Ca2+ level boosts calcitonin release which in turn decreases the concentration of Ca2+ in the blood by a) facilitating mineralization (bone) and b) reducing Ca absorption (intestine). If the Ca2+ level becomes too low, parathyroid hormone (PTH), an hormone antagonistic to calcitonin, is released. PTH increases the blood Ca2+ level by releasing calcium from bones again. The calcium level in blood is therefore controlled by a negative feedback loop.

For the effects of calcitonin see:
http://en.wikipedia.org/wiki/Calcitonin
http://www.mfi.ku.dk/ppaulev/chapter28/kap28.htm#6.%20Calcitonin
http://faculty.clintoncc.suny.edu/faculty/Michael.Gregory/files/Bio%20102/Bio%20...

For a definition of positive/negative feedback control see:
http://en.wikipedia.org/wiki/Positive_feedback

Best regards,
Christopher