Parathyroid Hormone

[StayingSteady]

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So if parathyroid hormone is involved in bone resorption and activation of Vitamin D (which I'm assuming is also involved in bone resorption), how come milk, which contains Vitamin D, aids in FORTIFYING bones?

 

[FutureInternist]

So if parathyroid hormone is involved in bone resorption and activation of Vitamin D (which I'm assuming is also involved in bone resorption), how come milk, which contains Vitamin D, aids in FORTIFYING bones?

Based on BRS physiology (Pg 284, 3rd ed) vit D does increase bone resorption but it is the "old" bone that is being resorbed to provide minerals for the "new" bone.
Vit D also --> increased absorption of Ca & PO4 from intestines & kidneys so the overall effect is to provide more minerals for bone making