6. Parathyroid gland and its hormones

Question 1

Name the hormone released by the parathyroid.

Answer 1

Parathyroid hormone (PTH)

Question 2

Which cells release PTH?

Answer 2

Chief cells

Question 3

What is the function of PTH?

Answer 3

Increases serum Ca2+ concentration.

Decreases serum PO4- concentration.

Question 4

What inhibits PTH secretion?

Answer 4

1. High serum Ca2+ concentration
2. Calcitriol (active vitamin D)
3. Severely low Mg2+ concentration

Question 5

Name the 3 ways PTH increases blood calcium levels.

Answer 5

1. Bones

Directly stimulating osteoblasts and thereby indirectly stimulating osteoclasts (through RANK/RANKL mechanism)

For bone reabsorption/breakdown and releases calcium

2. Intestines

PTH increases gastrointestinal calcium absorption by activating vitamin D

3. Kidneys

↑↑ calcium reabsorption from urine

Question 6

How does PTH regulate PO4- levels?

Answer 6

Via actions on the kidney

It is an inhibitor of proximal tubular reabsorption of PO4-.

Through activation of vitamin D, the absorption (intestinal) of PO4- is increased.

Decreases serum PO4- concentration.