Metabolic Bone Disease Flashcards
What are the two factors of bone strength?
Bone density (bone mineral density, BMD) and bone quality (architecture, damage)
What is osteoporosis?
Osteoporosis refers to a conditions where resorption > formation, osteoclasts > osteoblast activity.
Results in compromised bone strength predisposing to risk of fracture.
Define osteoporotic-related fragility fracture
Fracture from a fall from standing height or less
What are the attributing factors in osteoporosis?
- Imbalance in resorption and formation
- Age related (at 40y, resorption increases)
- Hormonal status (post-menopause)
- Calcium metabolism
- Physical activity
Compare type 1 and type 2 osteoporosis
Type 1 osteo = postmenopausal
- Trabecular bone - forearm, spinal fractures
Type 2 osteo = age related
- Cortical and trabecular bone (hip common)
Causes of secondary osteoporisis?
- Endocrine disease - e.g. Cushing’s, hyperparathyroidism
- Malabsorption
Describe the bone changes in osteoporosis
- Trabecular and cortical thinning and decrease in BMD
- Increased adipocytes in marrow
- No change in bone width
Common clinical presentation of osteoporosis
- Fractures - hip, vertebral bodies, forearm (radius)
- Microfractures
- Pain
What enzyme has markedly raised levels in osteoporosis?
Alkaline phosphatase (ALP)
What is the relationship between carboxy terminal telopeptide of type-1 collagen and osteoporosis?>
If levels are high - indicates secondary osteoporosis
What is the gold standard of diagnosis of osteoporosis?
Densitometry
What is Osteomalacia / Ricket’s?
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
What is the most common cause of osteomalacia/Rickets?
Severe vitamin D defeciency - impairs mineralisation, impairing quality/quantity of bone.
Clinical features of osteomalacia/Rickets
- Bone pain
- Bone deformities
- Fractures due to fragile bone
Levels of following in serum: calcium, phosphate, vitamin D and ALP?
Calcium, phosphate and vitamin D = low
ALP = high
Describe the relationship between hyperparathyroidism (primary and secondary) and bone resorption.
Primary (parathyroid adenoma/hyperplasia) and secondary (hypersecretion of PTH) results in stimulation of osteoclastic resorption
Results in:
- Hypercalcaemia
- Osteopenia
Clinical signs of hyperparathyroidism
Signs and symptoms of hypercalcaemia:
- Abdo cramps
- Constipation
- Muscle fatigue
- Renal calculi
Microscopic feature of hyperparathyroid related osteoclastic resorption
Tunnelling pattern - fibrous tissue replaces lost bone
What is Paget’s disease?
Unknown cause - disordered bone remodelling, resulting in thick, soft, porous and hypervascularised bone.
What are the three phases of Paget’s?
- Osteolytic - hyperactivated osteoclasts
- Mixed - lytic and blastic
- Osteoblastic - disordered new bone formation
Results in thick, soft, porous and hypervascularised bone.
What disease often presents with patients feeling ‘warm’ bones, and why?
Paget’s
Results in hypervascularisation of bone, resulting in a warm feeling.
Paget’s common sites and symptoms
Skull:
- Enlargement
- Cranial nerve compression
Spine
- Pain
- Cord compression
Femur/Tibia:
- Pain
- Deformity
- Path fracture
Diagnosis of Paget’s
X-ray, ALP levels
