CORTEX biochemistry Flashcards
What is osteoporosis?
Reduced bone mineral density and increased porosity
Osteoporosis can be described as a quantitive defect, what does this mean?
The bone is normal but there’s not enough of it
What does osteoporosis increase your risk of?
Fractures (i.e fragility fractures)
Define osteopenia and osteoporosis
Osteopenia - 1-2.5 SDs below mean
Osteoporosis - >2.5 SDs below mean
When does loss of bone density begin?
30 y/o
Describe physiological loss of bone density and mention the relevance of menopause
Slowdown of osteoblast activity with age
Increased osteoclastic bone reabsorption post-menopause due to reduced oestrogen
List the two types of primary bone osteoporosis
Type 1 post menopausal
Type 2 osteoporosis of old age
What are the risk factors for post menopausal osteoporosis?
Early menopause White people Smoking Alcohol Lack of exercise Poor diet
Which types of fractures tend to occur in post menopausal osteoporosis?
Colles fractures
Vertebral insufficiency
What are the risk factors for osteoporosis of old age?
Chronic disease Inactivity Reduced sunlight exposure (low vit D) Smoking Alcohol Poor diet White people
Which types of fractures tend to occur in osteoporosis of old age?
Femoral neck fractures
Vertebral fractures
List the causes of secondary osteoporosis
Corticosteroid use
Alcohol abuse
Malnutrition
Chronic disease (CKD, malignancy, rheumatoid arthritis)
Endocrine disease (cushing’s, hyperthyroidism, hyperparathyroidism)
How is osteoporosis diagnosed?
DEXA scanning
Normal serum calcium
Normal serum phosphate
How is osteoporosis managed?
Calcium supplements Vitamin D supplements Biphosphonates Monoclonal antibody (desunomab) Strontium
How is osteoporosis managed?
Exercise
Diet
Sunlight exposure
List some biphosphonates
Alendronate
Risedronate
Etdronate
IV zoledronic acid (once per year)
How do biphosphonates work?
Reduce osteoclast reabsorption
How does desunomab work?
Reduces osteoclast activity
How does strontium work?
Increases osteoblast replication and reduces absorption
Why is intranasal calcitonin not used to treat osteoporosis?
Increased cancer risk with no benefit over other treatments
HRT is recommended as first line treatment of osteoporosis in post menopausal women. T/F
False - considered if side effects with other medications
What are the risks of HRT?
Breast cancer
Endometrial cancer
DVT
What is raloxifene? What is the risk of it?
Oestrogen receptor modulator
DVT
Osteomalacia is a qualitative bone defect, what does this mean?
Bone quantity is normal but the quality is sub-par
What is osteomalacia?
Abnormal soft bones that have not been mineralised due to deficiencies in calcium and phosphorus
What is Rickets?
Abnormal soft bones that have not been mineralised due to deficiencies in calcium and phosphorus occuring in CHILDREN
What are the causes of osteomalacia and ricket’s?
Lack of dietary calcium
Deficiency of vitamin D
Resistance to vitamin D
Phosphate deficiency (increased renal loses)
What are the specific pathologies which lead to osteomalacia and ricket’s?
Malnutrition Malabsorption Lack of sunlight exposure Hydrophosphateamia Long term anti-convulsant use Chronic kidney disease
What are the causes of hydrophosphateamia?
Re-feeding syndrome
Alcohol abuse
Malabsorption
Renal tubular acidosis
Which inherited renal diseases can be the cause of osteomalacia and rickets?
X-linked hydrophosphateamia
Vitamin D resistant ricket’s
How does osteomalacia/ricket’s present?
Bone pain (pelvis, spine, femur)
Bony deformity
Pathological fractures
Hypocalcaemia
Is bony deformity more common in osteomalacia or ricket’s?
Ricket’s
How does hypocalcaemia present?
Paraesthesia Muscle cramps Irritability Fatigue Seizures Brittle nails
What may be typically seen on a radiograph of someone with osteomalacia or ricket’s?
Pseudofractures (looser’s zones) of pubic rami, proximal femur, ulna or ribs
How does osteomalacia/ricket’s present biochemically?
Low calcium
Low serum phosphate
High serum alk phosphatase
How is osteomalacia/ricket’s treated?
Vitamin D therapy
Calcium supplements
Phosphate supplements
What is hyperparathyroidism?
Over activity of parathyroid glands (i.e high parathyroid hormone)
What causes primary hyperparathyroidism?
Adenoma
Hyperplasia
Neoplasia
What is the result of primary hyperparathyroidism?
High PTH –> hypercalcaemia
How does primary hyperparathyroidism present biochemically?
High calcium
High PTH
Phosphate low/normal
How does hypercalcaemia present?
Bones (pain) Stones (renal) Groans (fatigue, depression) Myalgia Nausea Thirst Polyuria Osteoporosis
What is secondary hyperparathyroidism?
Overproduction of PTH secondary to hypocalcaemia caused by CKD or vit D deficiency
What is tertiary hyperparathyroidism?
Patients with chronic secondary hyperparathyroidism develop a parathyroid adenoma producing ectopic PTH
What is usually the cause of chronic secondary hyperparathyroidism?
CKD
What bone problems can hyperparathyroidism cause? How are they treated?
Fragility fractures
Brown’s tumours/osteitis fibrosa cystica (lytic bone lesions)
Stabilisation
How is hyperparathyroidism treated?
Removal of cause (e.g adenoma, cancer, etc)
Treatment of cause (e.g vit D deficiency, etc)
How is hypercalcaemia treated?
IV fluids
Biphosphonates
Calcitonin
What type of bone changes are caused by CKD? Why?
Secondary hyperparathyroidism causes osteomalacia, bone sclerosis and soft tissue calcification
Reduced phosphate excretion and inability to activate vit D
What is Paget’s disease?
Chronic bone disease causing thick, brittle and deformed bones
How many bones does paget’s disease affect? Which bones?
One or two
Pelvis, femur, skull, tibia
Which age groups are typically affected by Paget’s?
> 55 (increasing age)
Which two factors may increase incidence of Paget’s?
Viruses (paramyxoviruses)
Genetic defects
Describe the pathogenesis of Paget’s disease
Increased osteoclast activity (exaggerated vit D response) –>
Increased bone turnover –>
Osteoblasts become more active in a bid to compensate –>
New bone does not remodel correctly –>
Brittle, easily fractured bone
What happens if Paget’s occurs in ear ossicles?
Conductive deafness
How does Paget’s disease present?
Asymptomatic until picked up on x-ray Arthritis Pathological fractures Deformity Pain High output cardiac failure
How does Paget’s disease present biochemically?
High alk phosphatase
Normal calcium
Normal phosphate
How does Paget’s appear on an x-ray?
Enlarged bone with thickened cortices
Thickened trabeculae
Mixed lysis and sclerosis
How does Paget’s appear on bone scans?
Increased uptake in affected bones
How is Paget’s treated?
Biphosphonates
Calcitonin (extensive lysis)
Joint replacement
Femoral shaft fractures stabilised with IM nails
