Endo (pt 7/7) Bone Mineral Homeostasis Flashcards
___% of the 1-2 kg of Ca in the body is found in the bone.
98%
____% of the 1 kg of P in the body is found in the bone.
85%
How do Ca & P enter the body?
Via the intestine
How are Ca & P excreted?
Renally excreted to balance intestinal absorption
What are the three primary hormones of Ca & P homeostasis?
1) Parathyroid hormone (PTH)
2) Fibroblast Growth Factor 23 (FGF 23)
3) Vitamin D (prohormone)
What stimulates the production of the active metabolite of vitamin D (vit. D, 1,25 – dihydroxyvitamin D) in the Kidney?
Parathyroid Hormone (PTH)
What inhibits the production of 1,25 dihydroxyvitamin D by the kidney?
FGF23
1,25 dihydroxyvitamin D inhibits the production of ____ by the parathyroid glands, and stimulates release of ____ from the bone.
Parathyroid hormone; FGF23
What is the principal regulator of intestinal Ca & P absorption?
1,25 dihydroxyvitamin D
T/F: PTH and 1,25 dihydroxyvitamin D can only stimulate Osteoblast activity.
False; PTH & 1,25 vit D regulate bone formation and resorption. Each is capable of stimulating both processes (osteoblasts and osteoclasts)
Bone forming cells.
-Signaled by stem cells and preosteoblasts (and PTH and Active Vit D)
Osteoblasts
Break down bone.
-signaled by monocytes, and pre osteoclasts (and PTH and active Vit D).
Osteoclasts
What is the net effect of PTH secretion?
Increased Ca and Decreased P
What is the net effect of FGF23 Secretion?
Decreased P
What is the net effect of Vitamin D?
Increased Ca and P
What is the MOA of Calcitonin?
-Lower serum Ca & P by action on bone & kidney
-Inhibits osteoclastic bone resorption
-Reduces Ca & P reabsorption in the kidney
-Used in the treatment of: Paget’s disease, hypercalcemia, osteoporosis