biochemical disorders of bone Flashcards
what is osteomalacia/ Rickett’s
lack of mineralisation of osteoid (immature bone) resulting in abnormally soft bone (ricketts in children)
what causes osteomalacia (5)
insufficient calcium absorption, insufficient Vit D absorption/ production, post-menopause, phosphate deficiency, long term-anticonvulsants
what causes insufficient calcium absorption (osteomalacia)
lack of diet, defective absorption in GI tract
what causes insufficient vit D absorption (osteomalacia)
lack of sunlight/ vit D from diet (GI causes) causing secondary hyperparathyroidism (most common cause)
how does post menopause causes osteomalacia
lack of oestrogen
what causes can cause phosphate deficiency (osteomalacia)
renal disease, alcohol abuse
what are the symptoms of osteomalacia (4)
bone pain (pelvis, spine, femur), deformity (bowed legs, square head, pigeon chest), easily fractures, hypocalcaemia (cramp, fatigue, seizures)
what investigations can be done for ostoemalacia
X ray, biochem: low ca, low Vit D, low phosphate, high ALP and PTH
how do you treat osteomalacia
vit D replacement (Ca and phosphate supplements)
what is osteoporosis
decreased bone mineral density leading to increased risk of fracture with little trauma
what is the bone density of osteoporosis vs osteopenia
osteoporosis bone density 2.5SD below mean, osteopenia is intermediate stage and 1-2.4 SD below mean
what causes osteoporosis (6)
idiopathic, hyperparathyroidism, steroids, post menopause (loss of oestrogen and increased osteoclasts), old age, genes
what is type 1 osteoporosis
post menopausal –> increased osteoclast activity
what are risk factors for osteoporosis
smoking, white, alcohol, post menopause, sedentary, bad diet, vit D deficiency
what is type 2 osteoporosis
in elderly with greater density decline than normal
where do fractures usually occur in type 2 osteoporosis
femoral neck and vertebra
what are secondary causes of type 2 osteoporosis
endocrine (cushings and hyperparathyroidism), GI (malnutrition), drugs and alcohol (corticosteroids)
how do you diagnose osteoporosis
DEXA bone scan (gold standard), serum Ca and phosphate
what lifestyle measures can be used in osteoporosis management
exercise, increased Vit D in diet, sunlight
outline osteoporosis treatment
non curative, just slow progress. bisposphates –> desunomab –> stromium ranelate –> hormone replacement therapy (post menopausal women) (zolendronic acid)
what are bisphosphonates
reduce osteoclast activity eg alendronate
what is desunomab
monoclonal antibody that reduces osteoclasts
what is the use of zoledronic acid in osteoporosis
reduces fracture risk
what is hyperparathyroidism
too much PTH resulting in decreased calcium and phosphate in the bone by increasing osteoclasts
what stimulates PTH production
low serum Ca
what hormone opposed PTH
calcitrol from thyroid increases Ca absorption to bone
what are the symptoms of hyperparathyroidism
hypercalcaemia: bones, stones, abdo groans and psychic moans. (thirst, polyuria, N+V, depression, fractures)
what causes primary hyperparathyroidism, what is the biochem, and how do you treat it
adenoma, hyperplasia of parathyroid. biochem: raised Ca, PTH and ALP, remove surgically
what causes secondary hyperparathyroidism, what is the biochem, and how do you treat it
CKD or Vit D deficiency. biochem: high PTH, Ca low/normal, treat underlying cause
what causes tertiary hyperparathyroidism, what is the biochem, and how do you treat it
overactivity from longterm secondary hyperparathyroidism. biochem: high Ca and PTH. parathyroidectomy
hyperparathyroid management
treat underlying causes, bisphosphonates, cinacalct (ca mimic), HRT, parathyroidectomy (end stage)
what is Pagets disease
altered bone remodelling –> increased osteoclastic activity and bone turnover
what does Pagets lead to in the bone
cortical thickening, brittle bone, weakened and misshapen, soft tissue swelling
what can cause Paget’s disease
old age, metabolic disease, genetics, virus eg paramyxovirus
what are symptoms of Pagets
bone pain (pelvis, skull, spine, legs), arthritis and deformities, nerve compression, pathological fractures
how do you treat Pagets
bisphosphonates, joint replacement, (calcitonin)
what is avascular necrosis
bone infarction leading to necrosis of bone and bone marrow
how can AVN cause OA
patchy slcerosis –> subchondral collapse –> OA
what are common AVN sites
femoral head, humerus head, scaphoid
what can cause AVN
alcohol or steroid abuse, thrombus, sickle cell anaemia, SLE, secondary to fractures
how does alcohol and steroid abuse cause AVN
alters fat metabolism and promotes blood coagulation leading to compressed venous outflow
how to investigate and treat AVN
MRI>X ray, drill holes to decompress bones, joint replacement
which bone disease is qualitative
osteomalacia and rickett’s
which bone disease is quantitative
osteoporosis
