Page 1 of 1: Calcitonin & vit.D ?

spatil · Credits: 2263 My Scrapbook

We know that calcitonin tries to decrease the blood level of calcium as vit.D does but calcitonin increase excretion on other hand vit.D decrease excretion. Can anybody explain?

dr4jc · Credits: 4396 My Scrapbook

Calcitonin is secreted by the parafollicular cells of the thyroid gland when the serum calcium level goes above 9.5mg/dl....It is found to inhibit osteoclasts in vitro and thereby thought to lower blood calcium levels(refer Ganong).

VitD or rather 1,25 dihydroxycholecalciferol increase Calcium and phosphate reabsorption from the intestine by increasing Ca+-H+ ATPase molecules in the intestinal cells and these pump the Ca+ into the the interstitium...this also happens in the kidneys....In the bone it mobilises Ca and phosphate by increasing the mature osteoclasts. It also stimulates osteoblasts but the net effect would be mobilisation of calcium...(refer Ganong)

I dont know where you got your idea of "We know that calcitonin tries to decrease the blood level of calcium as vit.D does but calcitonin increase excretion on other hand vit.D decrease excretion".

spatil · Credits: 2263 My Scrapbook

OK. My ieda was to clear these things discussion i agree I haven't put that in right order. I know that calcitonin & vitD have different facets of action. I wanted someone to clear it in precise manner explaining interplay of calcitonin, vit.D & PTH.
We can say insimple words
-Main aim of vit.D is to increase calcium in bones for that it reduces excretion, increase absorption & move Ca from bones to blood.
-Main aim of calcitonin is to decrease blood Ca for that it increases excretion, decrease absorption & move Ca from blood to bones.
-PTH has exactly opposite action that of calcitonin.
Is it ok dr4jc ?

dr4jc · Credits: 4396 My Scrapbook

No calcitonin does not directly increase the excretion of calcium...it decreases the resorption of calcium from the bone..I hope you got that concept right

PTH on the other hand increases Calcium reabsorption from the kidney and increases phosphate excretion...So its not the exact opposite of calcitonin but increases the calcium levels in the serum...

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