Biochemical disorders of bone Flashcards
What is osteoporosis?
A quantitative defect of bone characterised by reduced bone mineral density and increased porosity i.e. the bone is of normal quality, there is just not enough of it
What is the risk associated with osteoporosis?
Increased risk of fracture with little or no trauma
What is the definition of osteoporosis on bone mineral density scan?
Less than 2.5 standard deviations below the mean peak value of young adults of same race and sex
What is osteopenia?
An intermediate stage where bone mineral density is between 1 to 2.5 standard deviations below mean peak value
What is type 1 osteoporosis?
Post‐Menopausal Osteoporosis with an exacerbated loss of bone in the post‐menopausal period
What increases risk & severity of type 1 osteoporosis?
Early menopause White/Caucasian Lack of exercise Smoking Alcohol abuse Poor diet
What is type 2 osteoporosis?
Osteoporosis of old age with a greater decline in bone mineral density than expected
What fractures are particularly likely with type 1 osteoporosis?
Colles fractures
Vertebral insufficiency fractures
What increases risk & severity of type 2 osteoporosis?
White/Caucasian Lack of exercise Smoking Alcohol abuse Poor diet Lack of vitamin D/sun exposure Chronic disease
Which fractures are particularly associated with type 2 osteoporosis?
Vertebral fractures
Femoral neck fractures
What conditions can osteoporosis occur secondary to?
Corticosteroid use
Alcohol abuse
Malnutrition
Chronic disease e.g. CKD, malignancy, rheumatoid arthritis
Endocrine disorders e.g. Cushing’s, hyperthyroidism, hyperparathyroidism
What happens to the levels of serum calcium and phosphate in osteoporosis?
They remain the same
What pharmacological treatments can be used to try and prevent further fragility in osteoporosis?
Calcium & vitamin D supplements
Bisphosphonates
Desunomab
Strontium
What are the names of some bisphosphonates and how do they help in osteoporosis?
Alendronate, risedronate, etidronate
Reduce osteoclastic resorption
What is desunomab?
A monoclonal antibody which reduces osteoclast activity
How does strontium help in osteoporosis?
Increases osteoblast replication and reduces resorption
What is osteomalacia?
A qualitative defect of bone with abnormal softening of the bone due to deficient mineralization of osteoid (immature bone) secondary to inadequate amounts of calcium and phosphorus
What is Ricket’s?
Osteomalacia in children: abnormal softening of bone due to inadequate amounts of calcium and phosphorus, resulting in deformity of the growing skeleton
What are the main causes of osteomalacia and rickets?
Insufficient calcium absorption from the intestine because of lack of dietary calcium or a deficiency of or resistance to the action of vitamin D
Phosphate deficiency caused by increased renal losses
What are some of the more specific causes of osteomalacia and ricket’s?
Malnutrition (Ca & vit D)
Malabsorption (low vit D absorption)
Lack of sunlight exposure
Hypophosphateamia (re‐feeding syndrome, alcohol abuse – impairs phosphate absorption, malabsorption, renal tubular acidosis)
Long term anticonvulsant use
Chronic kidney disease (reduced phosphate resorption & failure of activation vitamin D)
What are some of the presenting complaints of osteomalacia & rickets?
Bone pain in femur, pelvis or spine
Bone deformity (particularly in rickets)
Fractures easily
Symptoms of hypocalcaemia
What are some of the symptoms of hypocalcaemia?
Paraesthesiae Muscle cramps Irritability Fatigue Seizures Brittle nails
What serum bone biochemistry abnormalities can be seen in osteomalacia?
Low calcium
Low serum phosphate
High serum alkaline phosphatase
What is the treatment for osteomalacia and rickets?
Vitamin D and calcium supplements
What is hyperparathyroidism?
Overactivity of the parathyroid glands with high levels of parathyroid hormone
What are the causes of primary hyperparathyroidism?
Benign adenoma
Hyperplasia
Malignant neoplasia
What does high levels of hyperparathyroid hormone result in?
Hypercalcaemia
What are some of the symptoms of hypercalcaemia?
Fatigue Depression Bone pain Myalgia Nausea Thirst Polyuria Renal stones Osteoporosis
What does biochemistry show in hyperparathyroidism?
High levels of PTH
High levels of calcium
Phosphate normal or low
What are the causes of secondary hyperparathyroidism?
Secondary to hypocalcaemia:
Vitamin D deficiency
CKD
What is tertiary hyperparathyroidism?
A condition seen in patients with chronic secondary hyperparathyroidism (usually CKD) who develop an adenoma which will continue to produce PTH despite biochemical correction
What are some of the complications of hyperparathyroidism?
Fragility fractures
Lytic lesions in bone known as Brown tumours or osteitis fibrosa cystica which may need skeletal stabilisation
What is the treatment for hyperparathyroidism?
Removal of adenomatous gland
Treatment of underlying cause e.g. vitamin D supplementation
How is high levels of serum calcium treated?
As an emergency:
Iv fluid
Bisphosphonates
Calcitonin
What is Paget’s disease?
A chronic disorder which results in thickened, brittle and misshapen bones
What is the pathological process in Paget’s disease?
Increased osteoclast activity results in abnormally increased bone turnover
Osteoblasts try to correct this, forming new bone but failing to remodel the bone sufficiently
This results in increased thickness of bone with low density
How might Paget’s disease present?
Asymptomatic Incidental finding on Xray Arthritis Pathologic fractures Deformity Pain High output cardiac failure (due to increased blood flow through pagetic bone
Which bones are commonly affected by Paget’s disease?
Pelvis Femur Skill Tibia Ear ossicles
What are the radiographic features of Pagets disease
Enlarged bone
Thickened cortices
Coarse, thickened trabeculae
Mixed areas of lysis and sclerosis
What does biochemistry blood tests show in Paget’s disease?
Serum alk. phos. raised
Calcium normal
Phosphorus normal
How is Paget’s disease treated?
Bisphosphonates
Calcitonin if extensive lytic disease
