Parathyroid

Question 1

How many parathyroid glands are there?

Answer 1

4

Question 2

Where are they located in relation to the thyroid gland?

Answer 2

Posterior aspect of the thyroid gland

Question 3

Which cells secrete parathyroid hormone?

Answer 3

Chief cells

Question 4

What kind of hormone is parathyroid hormone?

Answer 4

A polypeptide

Question 5

What is the primary stimulus for parathyroid hormone?

Answer 5

Hypocalcaemia

Question 6

What is the primary inhibitor of parathyroid hormone?

Answer 6

Hypercalcaemia

Question 7

What is another name for a parafollicular cell?

Answer 7

C-cells

Question 8

What are parafollicular cells stimulated by?

Answer 8

Hypercalcaemia

Question 9

What are parafollicular cells inhibited by?

Answer 9

Hypocalcaemia

Question 10

Where is calcitonin produced from?

Answer 10

Parafollicular cells (or C -cells)

Question 11

What do parafollicular cells produce?

Answer 11

Calcitonin

Question 12

What stimulates calcitonin release?

Answer 12

Hypercalcaemia

Question 13

What stimulates parathyroid release?

Answer 13

Hypocalcaemia

Question 14

What is a humoral stimulus?

Answer 14

Endocrine function which is controlled by change in electrolytes i.e. hypocalcaemia leading to increased parathyroid release

Question 15

What kind of stimulus causes calcitonin or parathyroid release?

Answer 15

Humoral stimuli (calcium)

Question 16

How does PTH effect the bone?

Answer 16

Increase osteoclastic activity by activating osteoblasts to release Rank-ligand, which stimulates Rank receptors on osteoclasts

Question 17

What doe osteoclasts do?

Answer 17

Resorb bone - releases calcium into the blood

Question 18

What do osteoblasts do?

Answer 18

Bone deposition - takes calcium from the blood to build bone

Question 19

What is the significance of Rank Ligand to PTH?

Answer 19

Released by osteoblasts in response to PTH causing activation of the osteoclasts

Question 20

What is released by increased osteoclastic activity?

Answer 20

Phosphate and calcium

Question 21

How does PTH affect the blood biochemistry?

Answer 21

Increases phosphate and calcium release via increased osteoclastic activity, increased calcium uptake by kidney (phosphate is excreted) and increased synthesis of active vitamin D causing increased uptake in the GI tract of calcium

Question 22

How does PTH affect the kidney?

Answer 22

DCT to reabsorb calcium by secondary active transport + increases phosphate excretion + increases the expression of 1-alpha-hydroxalase

Question 23

What is the overall effect of PTH?

Answer 23

To increase calcium in the blood

Question 24

How is cholecalciferol formed?

Answer 24

UV light activates 7-dehydrocholestrol to cholecalciferol

Question 25

What happens to cholecalciferol in the liver

Answer 25

Converted to 25-hydroxycholecalciferol via 25-hydroxalase

Question 26

What is the role of 1-alpha-hydroxalase in the kidney?

Answer 26

It hydroxalases 25-hydroxycholecalciferol to | 1,25-cholecalciferol (calcitriol)

Question 27

What is another name for calcitriol?

Answer 27

Vitamin D

Question 28

How is Vitamin D produced?

Answer 28

UV light activates 7-dehydrocholesterol which goes to the liver and is converted to 25-hydroxycholecalciferol, which is converted by the kidney to 1,25-cholecalciferol, otherwise known as calcitriol or vitamin D)

Question 29

What is the role of Vitamin D?

Answer 29

Increase calcium uptake from the gi tract via calcium channel proteins

Question 30

What kind of hormone is vitamin D?

Answer 30

A steroid hormone

Question 31

Which mechanisms cause calcium increase by PTH?

Answer 31

Increased GI uptake via vitamin D, Increased osteoclast activity, Increase resorption of calcium in the kidney

Question 32

What is the overall effect of calcitonin?

Answer 32

Reduces blood calcium

Question 33

What does calcitonin do in the bone?

Answer 33

Directly inhibits osteoclastic activity and thereby increases osteoblastic activity

Question 34

Where do the parathyroid glands develop from in embryological development?

Answer 34

Superior glands - pharyngeal pouch 4 | Inferior glands - pharyngeal pouch 3

Question 35

What is the blood supply to the parathyroid gland?

Answer 35

Inferior and superior thyroid arteries

Question 36

Where is the gene for PTH located?

Answer 36

Chromosome 11

Question 37

What is the main cause of primary hyperparathyroidism?

Answer 37

A solitary adenoma of the parathyroid gland

Question 38

What is the main cause of secondary hyperparathyroidism?

Answer 38

Caused by hypocalcaemia secondary to chronic kidney disease or vitamin D deficiency

Question 39

What is the main cause of tertiary hyperparathyroidism?

Answer 39

Prolonged stimulation leads to hyperplasia of the parathyroid gland and insensitivity to calcium levels. This is seen in end stage renal failiure