Basic Science - Biochemistry Flashcards
What is osteoporosis?
Quantitative defect of bone due to reduced mineral density and increased porosity
What is the WHO definition of osteoporosis?
Mineral density of bone less than 2.5 standard deviations below mean peak value of young adults of same race and sex
What causes a loss in bone density?
Physiological after 30 due to slowing osteoblast activity
Females lose more after menopause due to loss of protective effect of oestrogen on osteoclastic bone resorption
What are the 2 types of osteoporosis?
Type 1 - post menopausal often due to early menopause + familial and environmental factors
Type 2 - Old age = greater fall in bone density than expected
What types of fractures are common in each type of osteoporosis?
Type 1
Colles fracture
Vertebral insufficiency
Type 2
Neck of femur
Vertebral fracture
Diagnosis of osteoporosis?
DEXA scan
Normal serum calcium and phosphate
Treatment of osteoporosis?
Calcium and Vitamin D supplementation
Bisphosphonates i.e. alendronate to reduce osteoclastic resorption . BEST AT PRESENT
Desunomab - monoclonal antibdy reducing osteoclast activity
Strontium
Intranasal calcitonin = no benefit and increased cancer risk
What is osteomalcia?
Qualitative defect of bone with softening due to deficient mineralisation of osteoid (immature bone) due to inadequate calcium and phosphorous
What are the causes of osteomalcia?
Lack of dietary calcium
Deficiency or resistance to action of Vitamin D
Phosphate deficiency due to renal loss
What are the signs and symptoms of Osteomalcia?
Bone pain (usually in pelvis, spine and femora)
Deformities from soft bone i.e. Rickets
Pathological fracture
Hypocalcaemia
i.e. muscle cramp, iritibility, fatigue , seizures
Investigations for Osteomalcia?
Biochemistry - low calcium, low serum phosphatase and high serum alk phos
Treatment for osteomalcia?
Vitamin D therapy + calcium/phosphate supplement
What is primary hyperparathyroidism?
Over production of PTH due to benign adenoma, hyperplasia or malignant neoplasia of parathyrod gland
What is secondary hyperparathyroidism?
Physiological overproduction of PTH secondary to hypocalcaemia usually caused by vitamin D deficiency or CKD ( due to reduced phosphate excretion and inactive activation of Vit. D)
What is tertiary hyperparathyroidism?
Chronic secondary developing an adenoma
What is the outcome of overproduction of PTH?
Hypercalcaemia
Phosphate normal
Bone manifestations of hyperparathyroidism?
Fragility fractures
Lytic lesions (Brown Tumours) - may need skeletal stabilisation
Treatment of hyperparathyroidism?
Removal of adenomatous gland
Vit D supplement
What is the treatment of very high serum calcium levels?
EMERGENCY
IV fluid
Bisphosphonates
Calcitonin
What is Paget’s disease?
Increased osteoclast activity results in increased bone turnover.
Osteoblast activity rises and form new bone
This fails to remodel sufficiently and the bone while thicker is brittle and prone to fracture
What are the causes of Pagets disease?
Virus - paramyxovirus
Genetic defect
What bones are most affected by Pagets disease?
Pelvis
Femur
Skull
Ear ossicles
How may Pagets disease present?
Incidental Arthritis Pathologic fracture Deformity Pain High output cardiac failure due to increased blood flow to pagetic bone
What would investigations show in Pagets disease?
Serum alk phos up, normal calcium and phosphorus.
Affected bone enlarged, thickened cortices and coarse, thick trabeculae
Mixed areas of lysis and sclerosis
Bone scan = marked increase in uptake at affected bone
What is the treatment of Pagets disease?
Bisphosphonates
Calcitonin if extensive lytic disease
