Hormone regulation calcium and phosphate

Question 1

What regulates calcium absorption?

Answer 1

PTH

Question 2

What senses change in serum calcium?

Answer 2

Chief cells

Question 3

What cause PTH release?

Answer 3

Low calcium lvls- stimulate PTH release

High calcium lvls- inhibit PTH release

Question 4

Does parathyroid hormone cause slow or fast response?

Answer 4

Fast response

Question 5

Mechanism of PTH?

Answer 5

Ca2+ binds to receptor
Intracellular cascade (Gq cascade)
Ca2+ released from ER

Question 6

State 4 effects of PTH?

Answer 6

1) IncreaseCa2+ reabsorption in kidneys- decreasing urinary Ca2+ excretion
2) Increases Ca2+ reabsorption in small intestine
3) Stimulates osteoclast break bone down- release Ca2+ and phosphorous
4) Stimulate formation of active form of vitamin D (1α,25-dihydroxyvitamin D)

Question 7

State 3 effects of vitamin D?

Answer 7

1) Amplify PTH
2) Stimulate vit D prod in kidney- cause Ca2+ and phosphate reabsorption
3) Stimulate osteoclasts break bone into Ca2+ and phosphate

Question 8

Function calcitonin?

Answer 8

Anti PTH

Question 9

What produces calcitonin?

Answer 9

Thyroid- C cells

Question 10

When is calcitonin released?

Answer 10

High plasma concentration of Ca2+

Question 11

What is released when high conc of Ca2+?

Answer 11

C cells of thyroid release calcitonin

Question 12

Effects of calcitonin?

Question 13

Where is vitamin D synthesised?

Answer 13

Skin- exposure to sunlight
Metabolised in liver and kidney to form 1α,25-dihydroxyvitamin D

Question 14

Outline how vitamin d is activated (flow diagram)

Answer 14

Question 15

How is vitamin D activated?

Answer 15

1) UV light hits skin
2) 7-dehydrocholesterol
3) Cholecalciferol (vit D3)
4) 25-hydroxylase catalyses reaction
5) 25-hydroxyvitamin D3 formed
6) 1-alpha-hydroxylase catalyses reaction
7) Forms 1,25-dihydroxyvitamin D3
(calcitrol)

Question 16

What is the active form of vitamin D called?

Answer 16

1,25-dihydroxyvitamin D3
(calcitrol)

Question 17

What enzyme is involved in cholecalciferol to 25 hydroxyvitamin D3?

Answer 17

25-hydroxylase

Question 18

What enzyme is involved in 25-hydroxyvitamin D3 to 1, 25 dihydroxyvitamin D3 (calcitrol)

Answer 18

1 alpha hydroxylase

Question 19

What sets off chain for activation of vit D3?

Answer 19

UV light hitting skin
Converts 7-dehydrocholesterol to cholecalciferol

Question 20

Where does the activation of vit D3 occur?

Answer 20

1) Skin
2) Liver (cholecalciferol to 25-hydroxyvitamin D3 (calcidiol))
3) Kidney (25 hydroxyvitamin D3 to 1,25 dihydroxyvitamin D3 (Calcitriol)

Question 21

Outline vit D3 formation?

Answer 21

1) Initially skin or diet
2) Vit D hydrolysed by liver by 25-hydroxylase to form 25-hydroxyvitamin D (calcidiol)
3) Kidney hydrolyses it using 1-hydroxylase to form 1,25-dihydroxyvitamin D (calcitriol)

Question 22

What stimulates hydrolysis of vit D3 in kidneys?

Answer 22

PTH

Question 23

What inhibits vit D3 activation?

Answer 23

High calcitriol- inhibit Pth

Question 24

What effects does calcitonin have?

Answer 24

1) Block PTH release
2) SI- inhibit Ca2+ absorption
3) Stop Ca2+ and phosphate release from bone
4) Kidney- inhibit Ca2+ reabsorption

Question 25

Give one function of bone related to Ca2+?

Answer 25

Storage (buffer) of Ca2+, Phosphate and magnesium

Question 26

Give 3 functions of kidney?

Answer 26

1) Respond Ca2+, PTH, vit D and calcitonin 2) Activate vit D 3) Regulate calcium and phosphate reabsorption/exc

Question 27

Function of parathyroid hormones?

Answer 27

1) Respond to changes in serum calcium 2) Synthesis and secretion PTH

Question 28

What stimulates PTH?

Answer 28

Low lvls serum calcium

Question 29

Function of GI tract?

Answer 29

1) Absorb Ca2+ and phosphate

Question 30

Function thyroid glands?

Answer 30

1) Respond changes in serum calcium 2) Synthesis and excretion of calcitonin

Question 31

What secretes calcitonin?

Answer 31

Thyroid glands

Question 32

Effect of PTH on: Intestine Kidney Bone Net effect serum lvl?

Answer 32

Intestine- increased calcium and phosphate absorption Kidney- decreased calcium excretion increased phosphate excretion Bone- calcium and phosphate resorption Serum- calcium increase, phosphate decrease

Question 33

Effect of vit D on: Intestine Kidney Bone Net effect serum lvl?

Answer 33

Intestine- increased Ca2+ and phosphate absorption Kidney- decreased excretion Bone- bone formation increased Serum- both increase

Question 34

What growth factor is involved in phosphate regulation? Function?

Answer 34

FGF23 Suppress phosphate reabsorption