Calcium Homeostasis

Question 1

What are the specific results of PTH?

Answer 1

Raise serum calcium (by resorption)

Lower serum phosphate

Question 2

How does PTH affect osteoclasts?

Answer 2

Increases number and activity of osteoclasts

Question 3

Is osteoclast stimulation a direct action of PTH?

Answer 3

No, it works on the Osteoblast to cause it to express RANKL

Question 4

What do small doses of PTH do to bone?

Answer 4

Increase bone formation without noticeable resorption

Question 5

What does PTH do in the kidney?

Answer 5

Increases reabsorption of Ca and Mg (positively charged ions)

Decreases reabsorption of Phosphate, AA, Bicarbonate, Sodium, Chloride, Sulfate (negatively charged ions)

Enhances conversion of Vit D to its active form

Question 6

Are there vascular smooth muscle and cardiac effects associated with PTH?

Answer 6

Yes

Question 7

What is hypoparathyroidism?

Answer 7

Parathyroid insufficiency - PTH not released due to malfunction of the gland

Question 8

What is Pseudohypoparathyroidsm?

Answer 8

PTH is released from the thyroid gland but target tissues are resistant (non-responsive)

Question 9

What is OPG?

Answer 9

A decoy receptor for RANKL. The OPG binds to the RANKL and prevents RANKL from binding to Osteoblast (it prevents resorption). OPG release is caused by estrogen.

Question 10

What is secondary hyperthyroidism?

Answer 10

Build up of PTH in people with chronic kidney failure.
Results in Vit D deficiency
Low calcium, high phosphorus, low active Vit D (vit D binds to vit D receptors in PTH gland to decrease release of PTH)

Question 11

What are the effects of Secondary hyperparathyroidism?

Answer 11

● Bone pain and nerve problems
● Itching
● Weak or brittle bones
● Skin breakdown
● Calcium build-up
● Resistance to therapy