Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Endocrinology > Endo 12 - Endocrine Bone Disorders > Flashcards

Endo 12 - Endocrine Bone Disorders Flashcards

1
Q

What is the common name given to the most important vitamin D metabolite?

A

Calcitriol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the chemical name of calcitriol?

A

1, 25-dihydroxycholecalciferol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the principle effect of calcitriol?

A

increases calcium, magnesium and phosphate absorption in the small intestine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the other effects of calcitriol?

A
  • increases calcium and phosphate reabsorption from the kidneys
  • stimulates osteoclast formation
  • stimulates osteoblasts to make osteoclast activating factors
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does Vitamin D deficiency cause?

A
  • lack of bone mineralisation
  • softening of bone - bowing of legs
  • bone deformities
  • bone pain
  • severe proximal myopathy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is vitamin D deficiency called in children?

A

rickets

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is Vitamin D deficiency called in adults?

A

Osteomalacia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Name 4 causes of vitamin D deficiency?

A
  • diet
  • lack of sunlight
  • GI malabsorption
  • renal failure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Which step in vitamin D metabolism requires UV light?

A

conversion of 7-dehydrocholesterol in the skin to form cholecalciferol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How many hydroxylation reactions are there in vitamin D metabolism?

A

2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe the 2 hydroxylation reactions in vitamin d metabolism?

A
  1. cholecalciferol hydroxylated to form 25-hydroxycholecalciferol in the liver
  2. hydroxylated by 1-hydroxylase to form 1,25 dihydroxycholecalciferol (calcitriol)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What can stimulate 1-hydroxylase in the kidneys?

A

Parathyroid hormone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How can lack of sunlight cause vitamin D deficiency?

A

will mean less 7-dehydrocholesterol gets converted into cholecalciferol in skin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How can liver disease cause vitamin D deficiency?

A

liver is where the first hydroxylation takes place

where 25-hydroxycholecalciferol is stored

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How can renal failure cause vitamin D deficiency?

A

where 2nd hydroxylation takes place

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is measured to gage the level of calcitriol?

A

25-Hydroxycholecalciferol

can only be used if normal renal function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How would you diagnose vitamin d deficiency?

A 
Plasma 25-hydroxycholecalciferol = low
plasma calcium = low
plasma PTH = high
plasma phosphate = low
radiology = widened osteoid seams
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What would the level of phosphate be in someone with renal failure?

A

High

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What would plasma calcium be in someone with renal failure?

A

Low - as not producing calcitriol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the consequence of hypocalcaemia caused by renal failure?

A

decrease in bone mineralisation
increase in bone resorption

= osteitis fibrosa cystica

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What can vitamin d excess lead to?

A

Hypercalcaemia and hypercalciuria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What does PTH do to bone?

A

Breaks it done in order to restore blood calcium level

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What can excess vitamin D result from?

A

excessive treatment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is Paget’s disease?

A

Very active, increased localised but disorganised bone metabolism
increased bone breakdown and formation

25
Q

What is Paget’s disease characterised by?

A

Abnormal large osteoclasts

26
Q

State some of the symptoms of Paget’s disease?

A 
- increased warmth over bones
increased osteoblast/osteoclast activity
- first osteoclast breaks bone down
- then osteoblast builds bone back up
- pelvis and femur most commonly affected
- increased chance of fracture
27
Q

Describe how you would diagnose Paget’s disease?

A

plasma calcium - normal
plasma ALP - high
radiology - spongy bone, increased bone density

28
Q

What are the two components of bone where 95% of body’s calcium is stored?

A
  1. Inorganic mineral component - 65%

2. Organic component - 35%

29
Q

What is the normal plasma calcium range?

A

2.2-2.6mmol/L

30
Q

State 2 hormones which increase plasma calcium?

A

PTH

Calcitriol

31
Q

Name a hormone that reduces plasma calcium?

A

Calcitonin

32
Q

What are the 2 direct effects of PTH?

A
  • Calcium mobilisation from bone

- increased calcium reabsorption in kidneys

33
Q

What are the 2 direct effects of calcitriol?

A
  • increased calcium absorption in small intestine

- increased mobilisation of calcium in bone

34
Q

What stimulates PTH release?

A

hypocalcaemia

35
Q

State 4 signs of hypocalcaemia?

A
  1. parasthesia
  2. arrhythmias
  3. convulsions
  4. tetany
36
Q

What effect does hypocalcaemia have on excitable tissue?

A

sensitises excitable tissue

37
Q

State 2 clinical signs of neuromuscular irritability due to hypocalcaemia?

A
  1. Chvostek’s sign - tap facial nerve just below zygomatic arch, twitching = positive response
  2. Trousseau’s sign = Pump blood pressure cuff for several minutes - +ve = carpopedal spasm
38
Q

State 4 causes of hypocalcaemia?

A
  • Hypoparathyroidism
  • vitamin d deficiency
  • pseudohypoparathyroidism
  • renal failure - imparied 1 hydroxylase
39
Q

Describe the effect of hypercalcaemia on neuronal excitability?

A

reduces neuronal excitability

40
Q

What are the signs of hypercalcaemia?

A
  • stones, groans and moans
  • stones - renal effects - polyuria and thirst
  • abdominal moans - anorexia, nausea, constipation
  • psychic groans - fatigue, depression, coma
41
Q

What are the 2 main causes of hypercalcaemia?

A
  • Primary hyperparathyroidism - e.g. adenoma

- Malignancy - bone tumours causing increased bone turnover

42
Q

How would you differentiate between primary hyperparthyroidism and malignancy?

A

Primary HPT would have no negative feedback so PTH will be high along with plasma calcium

Malignancy - plasma calcium high but PTH low

43
Q

Describe the treatment of vitamin D deficiency if normal renal function?

A

Give 25-hydroxy vitamin D

- patient can convert this to calcitriol using 1-hydroxylase

44
Q

Name the 2 types of supplements for vitamin D deficiency in normal renal function?

A
  • ergocalciferol

- cholecalciferol

45
Q

What is the treatment for vitamin D deficiency in patients with renal failure?

A

Alfacalcidol - 1-hydroxycholecalciferol

46
Q

What do osteocytes produce?

A

Type 1 collagen

47
Q

What is RANK ligand?

A

osteoclast activating factor
stimulates the maturation of osteoclast from precursors
so more bone resorption

48
Q

Define osteoporosis

A

Having a bone mineral density that is 2.5 standard deviations or more below the average for young healthy adults

49
Q

How is BMD measured?

A

DEXA scan

50
Q

State some pre-disposing conditions for osteoporosis?

A
  • post menopausal women
  • endocrine disease
  • hypogonadism in young people
51
Q

What are the advantages and disadvantages of estrogen replacement to prevent osteoporosis in post menopausal women?

A

adv - anti-resorptive effect in bone so prevents bone loss

dis - must be given with progesterone otherwise endometrial carcinoma

also breast cancer
VTE

52
Q

Name 2 oestrogen receptor modulators and their effects

A
  • Tamoxifen - oestrogenic in bone and anti-oestrogenic in breast and uterus SERM
  • Raloxifene - SERM - but causes stroke and VTE
53
Q

What is the 1st, 2nd and 3rd line treatment for osteoporosis?

A
  1. Bisphosphonates
  2. Denusomab
  3. Teriparatide
54
Q

What are bisphosphonates analogues of?

A

Pyrophosphate

55
Q

How do bisphosphonates work?

A

impairs ability of osteoclast to resorp bone
decreases maturation of osteoclasts
promotes osteoclast apoptosis

56
Q

State some uses of bisphosphonates?

A

Osteoporosis
malignanacy
paget’s

57
Q

State some of the unwanted effects of bisphosphonates

A

oesophagitis

flu like symptoms

58
Q

What is denusomab?

A

human monoclonal antibody
binds to RANKL and inhibits osteoclast formation
given every 6-12 months

59
Q

What is teriparatide?

A

recombinant PTH

INCREASES BONE RESORPTION and formation

Endocrinology (18 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions