Bone metabolism Flashcards
what hormones cause bone loss
glucocorticoids and prostaglandins
when is ALP produced
osteoblasts during the calcification of the osteoid matrix
difference between primary and secondary ossification centres
primary - long bones
secondary the epiphyseal plates
which zone gets the most blood supply around the physis plate
the zone of proliferation
definition of osteoporosis
decreased bone mass with normal composition and microstructure
Osteoporosis is due to
an imbalance of remodelling. There is relatively more resorption than bone formation.
Causes of osteoporosis
Age - post menopausal
Endo - ovarian failure, thyrotoxicosis, cushings, diabetes, hypogonadism.
Drugs - heparin, steroids, alcohol
General - immobilisation, weighlessness, carcinomatosis, malabsorption
definition of osteomalacia
insufficient mineralisation of osteoid and growth plate
What are the causes of osteomalacia and rickets?
Dietary
Due to primary lack of vitamin D or generalised malabsorption
Due to Inadequate endogenous calcitriol (1,25 hydroxycholecalciferol or 1,25-dihydroxycholecalciferol (1,25 DHCC))
Vitamin D deficiency leads to a decrease in
decrease in the amount of 1,25 DHCC synthesis, leading to a decrease in calcium and phosphate absorption from the gut.
Looser’s zones may be seen in what and radiologically as….
Osteomalacia
They are stress fractures (normal stress applied to abnormal bone). They consist of a narrow lucency seen perpendicular to the bone cortex. They are often symmetrical and bilateral, occurring in the neck of the femur, pubic rami, scapulae and lower ribs.
Features of bone resorption
Subperiosteal resorption (Fig 1) and occurs at the radial aspect of the middle and ring finger phalanges as well as the medial aspect of the tibia
Subligamentous resorption also occurs at the pubis and calvicle
Large areas of osteoclastic resorption causes large cortical, subcortical and medullary lucencies called Brown tumours.
