Week 1 Cortext - Biochemistry Flashcards
what are the characteristics of osteoporosis and what does this cause?
reduced bone mineral density
increased porosity (normal bone, just not enough of it)
leads to increased fragility and fracture risk
what is the WHO definition of osteoporosis?
bone mineral density less than 2.5 standard deviations below the mean peak value of young adults of same race and sex
what is osteopenia?
intermediate stage where bone mineral density is between 1-2.5 standard deviations below mean peak value
what causes loss of bone mineral density?
mostly a normal physiological process which starts around 30 years old with a gradual slowing of osteoblast activity
why do female tend to lose more bone mineral density?
after the menopause a loss of the protective effects of oestrogen results in an increase in osteoclastic bone reabsorption
what are the 2 types of osteoporosis?
post menopausal osteoporosis
osteoporosis of old age
what is post menopausal osteoporosis?
exacerbated loss of bone in the post menopausal period
risk factors include early menopause, smoking, alcohol, lack of exercise, poor diet, Caucasian race
what types of fractures typically appear in post menopausal osteoporosis?
colles fractures
vertebral insufficiency fractures
what is osteoporosis of old age?
greater decline in bone density with age than expected
risk factors similar to type 1 as well as chronic disease, inactivity and reduced sunlight exposure (vit D)
what types of fractures often appear in osteoporosis of old age?
femoral neck fractures
vertebral fractures
how else can osteoporosis occur?
secondary to other conditions corticosteroid use alcohol malnutrition chronic disease (cancer, rheumatoid arthritis etc) endocrine disease (cushings etc)
how is osteoporosis diagnosed?
DEXA scan (shows bone mineral density) Normal serum calcium and phosphate levels
can osteoporosis be cured?
no
treatments cant increase bone mineral density but can try and prevent further damage
how can osteoporosis be prevented?
by building up bone density via exercise, diet healthy sun exposure throughout life
how is osteoporosis treated?
bisphosphonates (1st line) - reduce osteoclastic reabsorption
Desunomab (monoclonal antibody which reduces osteoclast activity)
strontium (increases osteoblast replication and reduces absorption)
Yearly zoledronic acid injection
calcium and Vit D supplements
what treatment can be used if the other common ones cause side effects?
HRT
can help prevent post menopausal osteoporosis but gives increased cancer risk
what is osteomalacia?
qualitative defect of bone with abnormal softening of bone due to deficient mineralisation of osteoid (immature bone) secondary to inadequate amounts of calcium and phosphorus
what is rickets?
same as osteomalacia but occurs in children and can cause effects in growing skeleton
what causes osteomalacia/rickets?
insufficient calcium absorption from the intestines due to either lack of dietary calcium or deficiency/resistance to action of Vit D
OR
Phosphate deficiency caused by increased renal loss
name some specific causes of osteomalacia/rickets
malnutrition malabsorption lack of sunlight exposure hypophosphataemia long term anticonvulsant use chronic kidney disease
what are the signs and symptoms of osteomalacia/rickets?
bone pain (mainly pelvis, spine and femora)
soft bone deformities
easily fracture
symptoms of hypocalcaemia
what might a radiograph show in osteomalacia/rickets?
pseudofractures (loser’s zones), particularly in
- pubic rami
- proximal femora
- ulna
- ribs
what is seen in biochemistry of osteomalacia/rickets?
low calcium
low serum phosphate
high serum alkaline phosphatase
how is osteomalacia/rickets treated?
Vit D therapy
calcium and phosphate supplements
quantitative vs qualitative bone disorder?
quantitative = normal bone just not enough of it qualitative = bone quality not good
what is hyperparathyroidism?
overactivity of the parathyroid hormones causing high levels of parathyroid hormone (PTH)
what causes hyperparathyroidism?
benign adenoma, hyperplasia or rarely a malignant neoplasia of parathyroid glands
what does hyperparathyroidism cause?
hypercalcaemia and subsequent symptoms/signs
what are the signs and symptoms of hypercalcaemia?
fatigue depression bone pain myalgia nausea thirst polyuria renal stones osteoporosis
what can cause secondary hyperparathyroidism?
secondary overproduction of PTH due to hypocalcaemia (from Vit D deficiency or CDK)
what causes tertiary hyperparathyroidism?
when adenoma develops in people with chronic secondary hyperparathyroidism which continues to produce PTH despite biological correction
how does hyperparathyroidism appear on biochemistry?
high serum PTH
high calcium
normal/low phosphate
what complications can arise from hyperparathyroidism?
fragility fractures
lytic lesions in bone
- brown tumours
- osteitis fibrosa cystica
how is hyperparathyroidism treated?
lytic lesions may need skeletal stabilization
removal of adenomatous glands
treat cause - Vit D supplements etc
what is renal dystrophy?
reduced phosphate excretion and inactive activation of vit D results in secondary hyperparathyroidism with subsequent osteomalacia, sclerosis of bone and calcification of soft tissue
what is pagets disease?
increased osteoclast activity results in increased bone reabsorption
osteoblasts become more active to try and counteract this and produce new bone which fails to remodel properly
resulting bone is thickened, brittle, mis-shapen and can fracture easily
what can cause pagets disease?
viral infection
genetic defects
exaggerated response to Vit D
which bones are commonly affected in pagets disease?
pelvis femur skill tibia sometimes ear ossicles causing deafness
how does pagets disease present?
can be asymptomatic and only be seen on X ray
can cause arthritis
deformity, pain and fractures are common
high output cardiac failure can occur
what is seen on biochemistry in pagets disease?
raised serum alkaline phosphatease normal calcium and phosphorus imaging - enlarged bone - thickened cortices - coarse thickened trabeculae - mixed areas of lysis and sclerosis
how is pagets disease treated?
bisphosphonates (inhibit osteoclasts)
calcitonin if extensive lytic disease
joint replacement if needed
