Flashcards in Calcium & Bone Deck (47)
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1
Parathyroid glands and calcium
sense low serum calcium and increase PTH secretion
2
releases calcium and phosphorus
bone ultimately --> increases serum calcium
3
kidney and calcium
- increases calcitriol formation
- decreases excretion of calcium
4
small intestine
increases absorption of dietary calcium --> increases serum calcium
5
what induces parathyroid hormone release
hypocalcemia
6
parathyroid hormone
↑ serum Ca by increasing:
a. Formation of active 1,25 dihydroxyvitamin D3 in the kidney, which increases the absorption of calcium in the gut
b. Bone resorption of calcium
c. Kidney reabsorption of calcium (and increasing phosphate excretion)
7
teriparatide
Recombinant PTH: FDA approved for osteoporosis (given subcutaneously)
8
Vitamin D3 from the diet or from exposure to sunlight is hydroxylated to
25 hydroxyvitamin D3, calcifediol in the liver.
9
25 hydroxyvitamin D3, calcifediol in the liver...
a. This intermediate (hydrolyzed VD3 from diet or from sunlight exposure) is further hydroxylated in the kidney to 1,25 dihydroxyvitamin D3, calcitriol (Rocaltrol).
b. Dihydroxyvitamin D3 increases the intestinal absorption of calcium.
10
Effect of Calcitonin release and what triggers this?
calcitonin released in response to hypercalcemia, decreases bone resorption.
11
Vit D activation
➢ 7-Dehydrocholesterol
(Skin) ⇓ UV light
➢ Cholecalciferol(D3)
⇓ Liver
➢ Calcifediol 25(OH)D3
⇓ kidney
➢ *Calcitriol 1,25(OH)2D3
Calcitriol 1,25(OH)2D3 = Most active metabolite of vitamin D
12
Dihydroxyvitamin D3
increases the intestinal absorption of calcium.
13
Recombinant PTH: FDA approved for osteoporosis
teriparatide
14
Actions of Vitamin D
• ↑Absorption of Ca and Phosphate from intestine
• ↑ tubular reabsorption of calcium
• Help bone mineralization
15
Uses of Vit D
• Hypocalcemia caused by diseases -
• Nutritional rickets, hypoparathyroidism, renal disease, osteoprosis, amlabsorption
• Topical calcipotriene – used for treatment of psoriasis
16
Calcitonin
➢ Secreted by Parafollicular ‘C’ cells of thyroid
• Released in response to hypercalcemia and ↓ bone resorption
➢ Salmon calcitonin - i.m/s.c, nasal spray
➢ Actions
• Inhibits osteoclastic bone resorption
• Inhibits calcium and phosphate reabsorption in kidney
• ↓ serum calcium and phosphate
➢ Uses:
• Hypercalcemic states- Paget’s disease
• Post menopausal osteoporosis
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Uses of Calcitonin
• Hypercalcemic states- Paget’s disease
• Post menopausal osteoporosis
18
Actions of Calcitonin
• Inhibits osteoclastic bone resorption
• Inhibits calcium and phosphate reabsorption in kidney
• ↓ serum calcium and phosphate
19
Net effect of PTH
↓ Plasma PO4
↑ Plasma Ca
20
Net Effect of Vit D
↑ Plasma Ca
↑ Plasma PO4
21
Net Effect of Calcitonin
↓ Plasma PO4
↓ Plasma Ca
22
PTH's effect on Intestine
↑ Ca and ↑ PO4 absorption
23
PTH's effect on kidney
↓Ca and ↑ P04 excretion
24
PTH's effect on bone
↑ bone resorption (High dose, increasing osteoclasts)
↑ bone formation (Low dose by increasing osteoblasts)
25
Vit D's effect on Intestine
↑ Ca and P04 absorption
26
Vit D's effect on Kidney
↓Ca and PO4 excretion
27
Vit D's effect on Bone
↑ bone resorption
↑ bone formation
28
Calcitonin's effect on intestine
NONE
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Calcitonin's effect on kidney
↑ Ca and PO4 excretion
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