Understanding Calcium hemostasis when Hypocalcemia is Present

Hello, my colleagues,

I will be discussing calcium regulation today along with PTH

Normal Calcium level  : 10mg/dL or 5mEq/L or 2.5mmol/L

Calcium is regulated by Parathyroid hormone(PTH) which is secreted by the parathyroid gland.

A decrease in Calcium level in blood --> Activates PTH hormone --->> PTH hormone goes to

1) BONES - Activates osteoclasts and lyse the bone and release Ca+ and PO4- into blood

Ca which was released through lysing of the bone is bound along with P04 so it cannot be used as a free Ca, PTH does this unpairing of Ca and P04 with the help of Kidneys

2) KIDNEYS - Ca and Po4 gets filtered in the kidney, and usually PO4 gets reabsorbed in PCT of the kidney which is inhibited by PTH. Hence P04 gets excreted in the urine, whereas Ca2+ is reabsorbed in DCT, PTH increases this absorption,

So the net result is more calcium and less phosphate in the blood. It is free Ca2+(ionised Ca2+)

3) Finally, PTH also activates Vitamin D in the kidney, this Vitamin D goes into the gut and increases the further absorption of calcium and phosphate into the blood

Thus Calcium hemostasis is maintained through PTH when calcium levels go low

I will try to input more topics if you guys find it useful.