Parathyroid

Question 1

which cells produce PTH

Answer 1

chief cells

Question 2

What senses a change in serum calcium?

Answer 2

Calcium sensing receptor at parathyroid gland

Question 3

What happens when there is a decrease in calcium?

Answer 3

In kidney:
- increases Ca reabsorption and decreases PO4 reabsorption

In the bone:

• incr. osteoclasts
• incr. bone reabsorption releasing Ca

Question 4

What is hyperparathyroidism?

Answer 4

incr. blood Ca

Question 5

Cause of hyperparathyroidism

Answer 5

benign tumour on parathyroid gland adenoma
which causes the incr. of PTH secretion

As a result, incr. osteoclast, incr. bone reabsorption

End up with bone loss and incr. fracture risk

Question 6

what happens to elevation of bone active agent A

Answer 6

incr. bone resorption –> bone loss

Question 7

Bone active agent B

Answer 7

therapy to treat osteoporosis and incr. bone mass

Question 8

What is the main effect of Intermittent PTH

Answer 8

on osteoblasts
- anabolic effect on bone
levels last for 2-4 hrs

Question 9

Result of Intermittent PTH treatment

Answer 9

• incr. bone mass
• incr. bone connectivity
• decr. vertebral fracture risk
• decr. non-vertebral fracture risk

Question 10

mechanism of action of intermittent PTH

Answer 10

incr. the no. of osteoblasts (longer lifespan)

More become osteocytes

Question 11

What is dependent on PTH

Answer 11

• no. of new osteoclasts
• activity of osteoclasts
• lifespan of osteoclasts

Question 12

What is dependent on estradiol?

Answer 12

Formation

• no. of new osteoblast
• activity of osteoblast and life span

Question 13

purpose of estrogen and androgens (sex steroids)

Answer 13

help to maintain normal balance between bone formation and reabsorption

help to keep bone cells alive

Question 14

actions of estrogens in bone

Answer 14

• NB antiresorptive (prevent the reabsorption of bone)
• promote coupling
• increase formation

Question 15

estrogen deficiency

Answer 15

• incr. bone remodelling rate

- impaired bone formation (impaired coupling)

Question 16

Failure of coupling

Answer 16

estradiol enhances growth factor incorporation into bone matrix

Question 17

Consequence of reduced osteoblastic function with low estrogen

Answer 17

• less growth factor release = less signal to recruit and multiply osteoblasts
• imparied proliferation
• impaired functional activity
• reduced lifespan

Question 18

normal estrogen leads to:

Answer 18

Reduced bone resorption’8 ↓ osteoclast numbers)
via ‘increased ‘osteoprotegerin: ‘RANK8L’ production’(Obs)
via shorter osteoclast lifespan

Question 19

better coupling:

Answer 19

Increased osteoblastic (incr. in no. and incr. the lifespan)

Question 20

purpose of androgens

Answer 20

better bone geometry