Sunlight
I
Vitamin D
Livcr
Parathyroid chief cel
PTH
secretory
granules
Kidney
Ca2*
Ca2+
-ve feedback ♦
Bonę
1.25(OH)2 vitamin D (active)
25(OH) vitamin D (inactive)
r 25(OH) A vitamin D 1a-hydroxylase
Serum
calcium
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