Chemical Pathology 10 - Calcium metabolism Flashcards Preview

Year 5 Pathology ICSM - DM me for full access > Chemical Pathology 10 - Calcium metabolism > Flashcards

Flashcards in Chemical Pathology 10 - Calcium metabolism Deck (66)
Loading flashcards...
1

Around what percentage of the body's calcium is in the skeleton?

99%

2

What % of serum calcium is free/ionised?

50%

3

Which form of serum calcium is biologically active?

Ionised

4

Recall the 3 forms of serum calcium?

Free/ionised
Bound to albumin
Complexed with citrate/phosphate

5

What is "corrected calcium"?

Calcium corrected for albumin level

6

How can ionised calcium be measured?

Blood gas

7

What is the key role of circulating calcium?

Nerve and muscle function

8

Where in the body is calcium level detected for calcium homeostasis?

Parathyroid gland

9

Which cells are involved in releasing calcium from bone?

Osteoclasts

10

Recall the 3 ways in which PTH can act to increase serum calcium

1. Increase bone Ca resorption

2. Increase renal Ca resorption

3. Indirectly: increase 1-alpha hydroxylase action in kidneys - this increased vit D activation, and vit D increases gut absorption of vit D

11

What type of hormone is PTH?

Peptide hormone

12

What type of hormone is vitamin D?

Steroid hormone (derived from cholesterol)

13

What are the actions of PTH?

1. Increased resorption of calcium from bone and kidney

2. Renal phosphate wasting

3. Increase renal 1 alpha hydroxylase, which activates vit D

14

Recall the pathway of vit D synthesis

1. Cholecalciferol obtained from diet or converted by sunlight exposure from 7-dehydrocholesterol

2. 100% of absorbed cholecalciferol is converted to storage form (vit D3) in liver conversion by 25 hydroxylase

3. Activated by renal 1-alpha-hydroxylase - an enzyme under control of PTH - to the active form (1,25-(OH)2 D3)

15

Which hormone stimulates 1-alpha-hydroxylase production by the kidney?

PTH

16

In which disease can 1 alpha hydroxylase be produced outside the kidney, and where?

Sarcoidosis - in sarcoid lung tissue

17

Does sarcoidosis cause hypo or hypercalcaemia?

Hypercalcaemia

Sacroid tissue releases 1 alpha hydroxylase -->
Vit D activated outside the kidney --> calcium increased

18

Where is 1-alpha-hydroxylase produced in sarcoidosis?

Lung sarcoid tissue

19

What is calcitriol another name for?

1,25-dihydroxycholecalciferol

20

Where is 25 hydroxylase found?

Liver

21

What effect does 1,25(OH)2 vit D (active form) have on calcium and phosphate?

Increases calcium and phosphate absorption from intestines

22

Why is bone-specific ALP high when there is increased bone turnover?

Alkaline phosphatase pushes calcium and phosphate into bone

When it does this, some Alk phos is leaked into blood

Therefore, when you have increased bone turnover, you can measure the bone-specific AlkPhos in the blood and it will be high

23

Which electrolyte is necessary for PTH synthesis?

Magnesium

24

What is the difference between osteoporosis and osteomalacia in terms of bone structure and mass?

Osteoporosis = less bone of normal structure
Ostemalacia = normal amount of bone of wacky structure

25

What type of bone disease is caused by renal failure?

Renal osteodystrophy
1. Can't make 1 alpha hydroxylase --> lack of calcium absorption into bone
2. Can't excrete phosphate in kidney failure

26

Which conditions are caused by vit D deficiency in children and adults?

Children: Ricketts
Adults: osteomalacia

27

Recall 4 risk factors for vit D deficiency

Lack of sunlight exposure
Dark skin
Dietary
Malabsorption (eg coeliac)

28

Recall 4 clinical features of osteomalacia, including the biochemistry

Bone and muscle pain
Increased fracture risk
Looser's zone fractures
Biochem: low Ca and Pi, raised ALP

29

Recall 4 clinical features of Rickets

Bowed legs
Costochondral swelling
Widened epiphyses at the wrists
Myopathy

30

Why does chappati consumption increase vit D deficiency?

Phytic acid
(This chelates vit D in gut, adding to the vit D deficiency)

Decks in Year 5 Pathology ICSM - DM me for full access Class (85):