Bone Metabolism

Question 1

Amount of calcium in bone?

Answer 1

99%

Question 2

Amount of PO4 in bone?

Answer 2

85%

Question 3

PTH secreted by?

Answer 3

Chief cells of parathyroid gland

Question 4

PTH net effect on Ca and PO4

Answer 4

Increase Ca

Decrease PO4

Question 5

PTH stimulates OB to release? (3)

Answer 5

1. CK (IL1, IL6)
2. MCSF
3. RANKL

Question 6

PTH effect at kidney?

Answer 6

Increased conversion of 25 hyroxyvit D to 1,25 dihydroxy vit D
Calcium resorption
PO4 excretion

Question 7

PTH on intestines?

Answer 7

Indirectly increases Ca absorption through effect of 1,25 DH Vit D

Question 8

PTH structure?

Answer 8

84 amino acid peptide

Question 9

Calcitonin structure?

Answer 9

32 amino acid peptide

Question 10

Calcitonin produced by?

Answer 10

Parafollicles of thyroid gland - C Cells

Question 11

Calcitonin effect on OC?

Answer 11

Inhibition via receptor on OC

Question 12

Vit D structure?

Answer 12

Fat soluble secosteroid

Question 13

Vit D effect on bone and OC? (2)

Answer 13

1. Terminal differentiation of OC

2. Mineralization of osteoid matrix

Question 14

Estrogen function on bone?

Answer 14

Decreases bone resorption and remodelling

Question 15

Thyroid hormone function on bone?

Answer 15

At physis:

1. Stimulates chondrocyte growth
2. Type X collagen synthesis
3. ALP activity

Question 16

Growth hormone effect on serum calcium? (2)

Answer 16

Increased absorption

decreased urinary excretion

Question 17

Steroids increase bone loss by? (2)

Answer 17

1. decrease Ca absorption

2. decrease bone formation

Question 18

PTH inhibited by? (2)

Answer 18

Ca and Vit D