Session 11-Parathyroid And Calcium

Question 1

What is the normal serum calcium level?

Answer 1

2.2-2.6M

Question 2

How is 99% of calcium present in bone?

Answer 2

Hydroxyapatite crystals

Question 3

What are the three ways in which calcium levels are regulated?

Answer 3

• parathyroid hormone (PTH)
• dietary vit D
• calcitonin

Question 4

How does parathyroid hormone regulate calcium levels?

Answer 4

• stimulates bone resorption and release of calcium into circulation
• stimulates calcium reabsorption in kidney and excretion of phosphate

Question 5

How does dietary vit D regulate calcium levels?

Answer 5

• increases intestinal absorption of dietary calcium and renal reabsorption of calcium
• increases bone resorption

Question 6

How does calcitonin regulate calcium levels?

Answer 6

Counteracts effects of PTH so lowers serum calcium

Question 7

What is calcitriol?

Answer 7

Active form of vitamin D

Question 8

Which cells in the parathyroid gland produce PTH?

Answer 8

Chief cells

Question 9

What is the half life of PTH?

Answer 9

4 minutes

Question 10

True or false: chief cells degrade PTH as well as synthesise it

Answer 10

TRUE - PTH continually synthesised but little store

Question 11

What accelerates the cleavage of PTH in chief cells?

Answer 11

High serum calcium levels

Question 12

What effect does PTH have in the following organs:

1) bone
2) gut
3) kidney

Answer 12

1) increase resorption
2) activates vit D and hence increases transcellular uptake from GI tract
3) decreases loss of urine

Question 13

What is bone deposition?

Answer 13

Osteoblasts produce collagen matrix which is mineralised by hydroxyapatite

Question 14

What is bone reabsorption?

Answer 14

Osteoclasts produce acid micro-environment and hydroxyapatite dissolves