calcium and phosphate metabolism Flashcards
define and describe osteoporosis
loss of bone mass causes: endocrine malignancy drug-induced renal disease nutritional age
diagnosis of osteoporosis
measurement of bone mineral density
dual-energy xray absorbtiometry
t score = no. of SDs below average at peak bone density
z score = matched to age and/or group
status and bone mineral density
normal = T score of -1 or more
osteopenia = t score lower than -1 and >-2.5
osteoporosis = t score < or equal -2.5
severe osteoporosis = t score -2.5 and one/more fragility factor
endocrine causes of osteoporosis
hypogonadism = any cause of oestrogen deficiency
excess glucocorticoids = endogenous/exogenous
hyperparathyroidism
hyperthyroidism
treatments for osteoporosis
adequate calcium and vit d intake, appropriate exercise
post-menopausal
biphosphate = inhibits function of osteoclasts = riserdonate and alendronate
PTH analogues
denosumah = human monoclonal antibody against sclerostin
osteomalacia (rickets in children)
loss of bone mineralisation
permanent deformaties in bone growth diffuse aches and pains chronic fatigue weak bones low calcium, phosphate elevated alkaline phosphatase PTH may be elevated
cause of osteomalacia
vitamin D deficiency
mutations leading to errors in vitamin D metabolism
hypophosphataemia = treatment mainly involves ensuring adequate vit D and calcium
describe regulation of vitamin D
increased by:
PTH
low calcium
low pi
decreased by:
FGF-23 = inhibits calcitriol
high calcium
high phosphate
what is FGF-23
hormone secreted by osteocytes
phosphate balance = increases renal excretion
disorder:
oncogenic osteomalacia
x-linked hypophosphalemic rickets
autosomal dominant hypophosphatemic rickets
renal osteodystrophy
spectrual conditions associated with bone lesions in renal failure impaired pi excretion high plasma pi impaired vit D activation low plasma ca PTH rises excess bone resorption may be augmented by acidosis
