Metabolic Bone Disease

Question 1

What are the two factors of bone strength?

Answer 1

Bone density (bone mineral density, BMD) and bone quality (architecture, damage)

Question 2

What is osteoporosis?

Answer 2

Osteoporosis refers to a conditions where resorption > formation, osteoclasts > osteoblast activity.

Results in compromised bone strength predisposing to risk of fracture.

Question 3

Define osteoporotic-related fragility fracture

Answer 3

Fracture from a fall from standing height or less

Question 4

What are the attributing factors in osteoporosis?

Answer 4

• Imbalance in resorption and formation
• Age related (at 40y, resorption increases)
• Hormonal status (post-menopause)
• Calcium metabolism
• Physical activity

Question 5

Compare type 1 and type 2 osteoporosis

Answer 5

Type 1 osteo = postmenopausal

• Trabecular bone - forearm, spinal fractures

Type 2 osteo = age related

• Cortical and trabecular bone (hip common)

Question 6

Causes of secondary osteoporisis?

Answer 6

• Endocrine disease - e.g. Cushing’s, hyperparathyroidism
• Malabsorption

Question 7

Describe the bone changes in osteoporosis

Answer 7

• Trabecular and cortical thinning and decrease in BMD
• Increased adipocytes in marrow
• No change in bone width

Question 8

Common clinical presentation of osteoporosis

Answer 8

• Fractures - hip, vertebral bodies, forearm (radius)
• Microfractures
• Pain

Question 9

What enzyme has markedly raised levels in osteoporosis?

Answer 9

Alkaline phosphatase (ALP)

Question 10

What is the relationship between carboxy terminal telopeptide of type-1 collagen and osteoporosis?>

Answer 10

If levels are high - indicates secondary osteoporosis

Question 11

What is the gold standard of diagnosis of osteoporosis?

Answer 11

Densitometry

Question 12

What is Osteomalacia / Ricket’s?

Answer 12

Osteomalacia / Ricket’s is defective mineralisation of organic matrix leading to bone softening.

Rickets = children

Osteomalacia = adults

Reduced strength and rigidity makes bones susceptible to compressible forces - Bowed legs in Rickets

Question 13

What is the most common cause of osteomalacia/Rickets?

Answer 13

Severe vitamin D defeciency - impairs mineralisation, impairing quality/quantity of bone.

Question 14

Clinical features of osteomalacia/Rickets

Answer 14

• Bone pain
• Bone deformities
• Fractures due to fragile bone

Question 15

Levels of following in serum: calcium, phosphate, vitamin D and ALP?

Answer 15

Calcium, phosphate and vitamin D = low

ALP = high

Question 16

Describe the relationship between hyperparathyroidism (primary and secondary) and bone resorption.

Answer 16

Primary (parathyroid adenoma/hyperplasia) and secondary (hypersecretion of PTH) results in stimulation of osteoclastic resorption

Results in:

• Hypercalcaemia
• Osteopenia

Question 17

Clinical signs of hyperparathyroidism

Answer 17

Signs and symptoms of hypercalcaemia:

• Abdo cramps
• Constipation
• Muscle fatigue
• Renal calculi

Question 18

Microscopic feature of hyperparathyroid related osteoclastic resorption

Answer 18

Tunnelling pattern - fibrous tissue replaces lost bone

Question 19

What is Paget’s disease?

Answer 19

Unknown cause - disordered bone remodelling, resulting in thick, soft, porous and hypervascularised bone.

Question 20

What are the three phases of Paget’s?

Answer 20

1. Osteolytic - hyperactivated osteoclasts
2. Mixed - lytic and blastic
3. Osteoblastic - disordered new bone formation

Results in thick, soft, porous and hypervascularised bone.

Question 21

What disease often presents with patients feeling ‘warm’ bones, and why?

Answer 21

Paget’s

Results in hypervascularisation of bone, resulting in a warm feeling.

Question 22

Paget’s common sites and symptoms

Answer 22

Skull:

• Enlargement
• Cranial nerve compression

Spine

• Pain
• Cord compression

Femur/Tibia:

• Pain
• Deformity
• Path fracture

Question 23

Diagnosis of Paget’s

Answer 23

X-ray, ALP levels