Calcium & Bone Flashcards

1
Q

Parathyroid glands and calcium

A

sense low serum calcium and increase PTH secretion

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2
Q

releases calcium and phosphorus

A

bone ultimately –> increases serum calcium

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3
Q

kidney and calcium

A
  • increases calcitriol formation

- decreases excretion of calcium

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4
Q

small intestine

A

increases absorption of dietary calcium –> increases serum calcium

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5
Q

what induces parathyroid hormone release

A

hypocalcemia

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6
Q

parathyroid hormone

A

↑ 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)

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7
Q

teriparatide

A

Recombinant PTH: FDA approved for osteoporosis (given subcutaneously)

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8
Q

Vitamin D3 from the diet or from exposure to sunlight is hydroxylated to

A

25 hydroxyvitamin D3, calcifediol in the liver.

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9
Q

25 hydroxyvitamin D3, calcifediol in the liver…

A

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.

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10
Q

Effect of Calcitonin release and what triggers this?

A

calcitonin released in response to hypercalcemia, decreases bone resorption.

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11
Q

Vit D activation

A
➢ 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

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12
Q

Dihydroxyvitamin D3

A

increases the intestinal absorption of calcium.

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13
Q

Recombinant PTH: FDA approved for osteoporosis

A

teriparatide

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14
Q

Actions of Vitamin D

A
  • ↑Absorption of Ca and Phosphate from intestine
  • ↑ tubular reabsorption of calcium
  • Help bone mineralization
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15
Q

Uses of Vit D

A
  • Hypocalcemia caused by diseases -
  • Nutritional rickets, hypoparathyroidism, renal disease, osteoprosis, amlabsorption
  • Topical calcipotriene – used for treatment of psoriasis
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16
Q

Calcitonin

A

➢ 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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17
Q

Uses of Calcitonin

A
  • Hypercalcemic states- Paget’s disease

* Post menopausal osteoporosis

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18
Q

Actions of Calcitonin

A
  • Inhibits osteoclastic bone resorption
  • Inhibits calcium and phosphate reabsorption in kidney
  • ↓ serum calcium and phosphate
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19
Q

Net effect of PTH

A

↓ Plasma PO4

↑ Plasma Ca

20
Q

Net Effect of Vit D

A

↑ Plasma Ca

↑ Plasma PO4

21
Q

Net Effect of Calcitonin

A

↓ Plasma PO4

↓ Plasma Ca

22
Q

PTH’s effect on Intestine

A

↑ Ca and ↑ PO4 absorption

23
Q

PTH’s effect on kidney

A

↓Ca and ↑ P04 excretion

24
Q

PTH’s effect on bone

A

↑ bone resorption (High dose, increasing osteoclasts)

↑ bone formation (Low dose by increasing osteoblasts)

25
Q

Vit D’s effect on Intestine

A

↑ Ca and P04 absorption

26
Q

Vit D’s effect on Kidney

A

↓Ca and PO4 excretion

27
Q

Vit D’s effect on Bone

A

↑ bone resorption

↑ bone formation

28
Q

Calcitonin’s effect on intestine

A

NONE

29
Q

Calcitonin’s effect on kidney

A

↑ Ca and PO4 excretion

30
Q

Calcitonin’s effect on bone

A

↓ bone resorption

31
Q

Estrogens effect on Calcium and bone

A
  • Inhibition of PTH stimulated bone resorption

* Use in postmenopausal osteoporosis

32
Q

Glucocorticoids effect on Calcium and bone

A

➢ Antagonize the vitamin D stimulated intestinal calcium absorption
➢ Stimulate renal calcium excretion
➢ Prolonged administration- can cause osteoporosis in adults and stunted growth in children

• Use: reversing hypercalcemia in lymphomas, sarcoidosis

33
Q

Bisphosphonates MOA

A
  • Retard the formation and dissolution of hydroxyapatite crystals in bone
  • Inhibit osteoclast mediated bone resorption
34
Q

Bisphosphonates

A

➢ Etidronate , Alendronate

➢ Pamidronate, Residronate, Zolendronate

35
Q

Bisphosphonates Uses

A
  • Postmenopausal Osteoporosis
  • Hypercalcemia associated with malignancy
  • Paget’s disease
36
Q

Bisphosphonates A/E

A
  • Gastric irritation (Except etidronate)
    * Tell patient to take drug with pleanty of water and sit in an upright position for 20-30 minutes following drug (bc causes reflux esophagitis)
  • Esophageal ulceration
37
Q

Plicamycin (Mitramycin)

A
Cytotoxic antibiotic 
•  Reduce serum calcium levels and bone resorption 
➢ Use :
•  Pagets disease 
•  Hypercalcemia
38
Q

Thiazide diuretics

A

➢ Increased calcium reabsorption from renal tubules (acts at DCT)
➢ Use: Idiopathic hypercalciuria

39
Q

Causes of Hypercalcemia

A
  • Hyperparathyroidism
  • Malignancy
  • Hypervitaminosis
  • Sarcoidosis
40
Q

Hypercalcemia Treatment

A
  • Rehydration with saline and diuresis with furosemide
  • Pamidronate/zoledronate - hypercalcemia in malignancy
  • Calcitonin
  • Plicamycin
  • Glucocorticoids - hypercalcemia in sarcoidosis
41
Q

Causes of Hypocalcemia

A
  • Hypoparathyroidism
  • Vitamin D defeciency
  • Chronic kidney disease
  • Malabsorption
42
Q

Treatment for Hypocalcemia

A
1. Calcium
➢ IV:
•  Calcium chloride			
•  Calcium gluconate*
•  Calcium gluceptate 	
➢ Oral:
•  Calcium lactate
•  Calcium carbonate
•  Calcium citrate
  1. Vitamin D: Calcitriol
43
Q

Osteoporosis:
• Def
• Causes

A

➢ Abnormal loss of bone predisposing to fractures
➢ Causes
• Postmenopausal
• Long term use of glucocorticoids, heparin, thiazides, phenytoin
• Thyrotoxicosis
• Hyperparathyroidism

44
Q

Treatment for Osteoporosis

A
  • Hormone Replacement Therapy = Estrogen + progesterone
  • SERMs = Raloxifene
  • Teriparatide
  • Bisphoshonates = Alendronate, residronate
  • Other treatment options:
    • Calcitonin, Vitamin D, Calcium
45
Q

Paget’s Disease of Bone
• def
• diagnosis

A

➢ Localized bone disease characterized by uncontrolled bone resorption with secondary new bone formation

➢ Diagnosis:
• Elevated serum alkaline phosphatase
• Urinary hydroxyproline levels
• abnormal bones on Xray

46
Q

Treatment for Paget’s Disease of Bone

A
  • Calcitonin
  • Bisphosphonates:
    * Etidronate
    * alendronate
    * residronate
47
Q

calcipotriene

A

Topical VitD: used for treatment of psoriasis