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Human Diseases > HD 7 - Metabolic bone disorders > Flashcards

HD 7 - Metabolic bone disorders Flashcards

1
Q

How much Ca does the kidney filter and excrete per day?

A

Glomerular filters 10g a day

0.2g out of kidneys

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2
Q

How much Ca is needed for bone remodelling/repair per day?

A

0.5g per day

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3
Q

How much Ca is found in the body?

A

1kg

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4
Q

Where is the vitamin D3 found?

A

Formed from action of sunlight in the skin with cholesterol, some from meat + fish

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5
Q

How does the liver process vitamin D3?

A

Liver hydroxylates vit D3 + stored in the liver as 25-vit D3

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6
Q

What forms of vitamin D3 does the kidney convert?

A

Conversion of 25-D3 –> 1,25-D3 (ACTIVE hormonal form)

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7
Q

What happens to PTH levels when Ca is low and high?

A

Low Ca –> Increased PTH

High Ca –> Decreased PTH

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8
Q

What happens to the bone health in chronic high PTH?

A

Bones gradually deteriorate and release Ca

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9
Q

Where is the biggest source of Ca in the body?

A

BONES

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10
Q

What is the function of osteoclasts?

A

Absorb bone (and apoptose after function fulfilled)

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11
Q

What is the function of osteoblasts?

A

Reform new bone with calcium

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12
Q

What is the function of osteocytes?

A

Resting bone

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13
Q

What is Ca bound to in the body?

A

1/2 bound to albumin (protein)

1/2 ionised (active form regulated by PTH)

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14
Q

What biochemistry is increased in fracture healing?

A

Alkaline phosphatase, due to increased osteoblast

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15
Q

When is alkaline phosphatase raised in the body?

A

In fracture healing, due to increased osteoblast activity

Also in liver problem

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16
Q

What is the function of albumin in the blood?

A

Ca transporter

Low albumin can result in lower Ca levels

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17
Q

What are the phosphate levels in kidney failure?

A

High

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18
Q

Where is phosphate found?

A

Meat

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19
Q

What are examples of bone turnover markers in blood/urine?

A

DPD or CTX

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20
Q

What do beta cross laps levels measure?

A

Measure osteoclastic activity and breakdown product of bone collagen

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21
Q

What do x-rays show in bones?

A

Metastases, deformities & fractures

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22
Q

What does a MRI show in bones?

A

Water not Ca

23
Q

What does radioisotope scanning show in bones?

A

Taken up by osteoblasts, shows hotspot areas of increased turnover

Not diagnostic but can indicate an abnormality

24
Q

What does DEXA stand for?

A

Dual energy X ray absorptiometry

25
Q

What does DEXA measure?

A

Assesses bone mineral density for diagnosis of osteoporosis

26
Q

What is the main cause for primary hyperparathyroidism?

A

Adenoma

27
Q

What does secondary hyperparathyroidism mean?

A

PTH working normally

Low normal calcium, high PTH = normal response

28
Q

What does a vitamin D deficiency cause in kids and in adults?

A

Kids - rickets

Adults - osteomalacia

29
Q

What can cause rickets?

A

Vitamin D deficiency
Phosphaturia (genetics)
Low Ca intake
Poor diet and sunlight exposure

30
Q

What happens to the bones in rickets?

A

Swollen bones at epiphyses
Enlarged costalchondral junction
Harrison’s sulcus - ribs deformed - diaphragm pulled in on the ribs

31
Q

What are the symptoms of osteomalacia?

A

Bone pain, muscular weakness, malaise, rarely tetany

32
Q

Why would tetany present in osteomalacia?

A

Tetany = calcium stabilises muscles membranes – pain and tremors
Hand of obstetrician

33
Q

What are the levels of Ca, PTH, Phosphatase and ALP in osteomalacia?

A

Ca - low
PTH - high
Phosphatase - low
ALP - high

34
Q

How is osteomalacia treated?

A

Vitamin D replacement and rectifying underlying cause – normally given orally

35
Q

What vitamin D medications are available?

A
  • Vitamin D depot injection 300,000 units every 6-12 months
  • Dekristol (trade name) – 20,000 units of vit D
    • Big dose – severely deficient or building up stores
    • Given weekly or monthly; increasingly used in our area.

• Fultium D3 – formulation of 800 units – smaller tablet you can chew (1/2 a day)

36
Q

What is Paget’s disease?

A

Uncoordinated bone re-modelling and disorganised bone turnover

37
Q

What are the symptoms of Paget’s disease?

A
  • Pain, deformity, increased fracture risk, compression of nerves
  • In skull, causes cranial nerve palsies. Can also cause fuzzy and thickened skull on x-ray
  • Commonest nerve problem is in the auditory nerve = causing deafness
38
Q

What is the treatment for Paget’s disease?

A

Bisphosphonates

Most commonly alendronic/ risedronic acid

39
Q

What is the function of bisphosphonates?

A

Inhibit osteoclastic activity and prevent bone resorption

40
Q

What is osteoporosis?

A

Reduced bone density impaired structure and increased risk of fracture

41
Q

What are common fracture sites in osteoporosis?

A

Wrist, vertebrae and neck of femur

42
Q

Why is osteoporosis more common in women?

A

Menopause, lacking oestrogen causing more rapid bone deterioration

43
Q

What causes osteoporosis?

A
  • Age
  • Post-menopausal, early menopause
  • Steroid treatment = Cushing syndrome (most often cause - iatrogenic)
  • Chronic liver, kidney, nutritional disorders affecting Ca and vit D
44
Q

What are the treatments for osteoporosis?

A

• Bisphosphonates (low dose)
– Alendronate or risedronate orally weekly
– Ibandronate or zoledronate by injection quarterly or annually

• HRT and oestrogen analogues

  • Help prevent the effect of menopause
  • Controversial due to breast cancer/thrombosis risk
  • Ca and D3 in malnourished elderly
  • Denosumab – monoclonal antibody against cytokine, sc injection 6 monthly (BIOLOGIC) = causes hypocalcaemia
  • PTH injections – daily s-c injection, expensive – puts calcium into bones
45
Q

How do bone metastases develop?

A

Development of secondary malignant growths at a distance from a primary site of cancer

46
Q

Where is the most common site of bone metastases?

A

Breast, lung and phosphate

47
Q

What is myeloma?

A

Malignancy of plasma cells in bone marrow

48
Q

What occurs to the bone in myeloma?

A

Stimulates osteoclasts but not osteoblasts

49
Q

What are the symptoms associated with myeloma?

A
  • Causes bone pain, fracture, pressure on adjacent nerves, spinal cord
  • Spinal cord compression – paraplegia – medical emergency
  • Hypercalcaemia of malignancy can occur with or without bone metastases
50
Q

What presents in the pelvis from breast cancer metastases?

A

Holes in pelvis, lytic in bone

51
Q

What is the treatment of bone metastases?

A

• Radiotherapy – relieve bone pain
• Surgery for complications – fracture/ compression
• Pain relief for symptoms
• High dose IV bisphosphonates can reduce progression in myeloma, breast and prostate cancer
- Can use Denosumab in a similar way

52
Q

How does phossy jaw come about in the body?

A

Exposed to phosphorus

53
Q

When does osteonecrosis of the jaw occur?

A
  • Case series of cancer patients
  • All on high dose bisphosphonates for Paget’s disease, myeloma, hypercalcaemia
  • Can occur with Denosumab
  • Majority had had dental or maxillo-facial surgery

Human Diseases (17 decks)

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