Calcium homeostasis

Question 1

Where in the body is calcium stored?

Answer 1

Bone (99%)

Plasma - bound to protein

Plasma - unbound (free/ionised)

Question 2

How is the plasma calcium level regulated?

Answer 2

PTH - increases Ca²⁺ by mobilising it from bone.

Calcitonin - decreases Ca²⁺ by inhibiting resorption from bone

1,25-dihydroxycholecalciferol - increases Ca²⁺ by increasing absorption from intestines and kidneys

Question 3

How does bone resorption occur?

Answer 3

Osteoclasts develop in response to RANKL, and cause dissolution of hydroxyapatite and collagen.