13) Endocrine & metabolic bone disorders Flashcards
What % of Ca2+ is stored in bone?
95%
How is Ca2+ release from bone stimulated?
PTH
2 components of bone:
Organic (35%)=osteoid
Inorganic (65%)=calcium hydroxyapatite crystals
What type of bone is on the inside + outside?
Outside=cortical (hard)
Inside=trabecular (spongy)
What pattern is bone normally vs when trying to heal?
Normally: lamellar
Heal=woven (disorganised)
2 cells involved in bone remodelling:
Osteoblasts=make bone
Osteoclasts=breakdown bone
How are osteoclasts and osteoblasts linked?
Osteoblasts activate osteoclasts
RANKL on osteoblasts binds to RANKLR on oesteclasts=activates them
2 receptors on osteoblasts:
PTH + Calcitriol
What is VIT D deficiency in adults vs children?
Children: rickets
Adults: osteomalacia
Compare primary, secondary and tertiary hyperparathyroidism:
Primary (high Ca2+, high PTH, low PO43-)
- adenoma
- parathyroid glands secrete lots of PTH=Ca2+ increases
- loss of -ve feedback
Secondary (high PTH)
- VIT D deficiency so Ca2+ levels fall so PTH levels rise
- renal failure
Tertiary
- Begins with secondary hyperparathyroidism then over time all 4 parathyroid glands get bigger
- negative feedback is lost & they become autonomous
What causes brown tumours?
High PTH causing excess bone breakdown
What happens in osteoporosis:
Loss of bony trabeculae (T score=-2.5 or less)
What do both osteomalacia and osteoporosis predispose to?
Fracture
Compare osteomalacia and osteoporosis:
Osteomalacia
- abnormal biochemistry (low VIT D, low Ca2+, high PTH)
- inadequate bone mineralisation
- diagnosed with blood test
Osteoporosis
- normal biochemistry
- decreased bone mass
- diagnosed with DEXA scans
What effects does oestrogen have for post menopausal women?
Prevent osteoporosis
Increase risk of stroke + breast cancer
Progesterone must be given alongside to reduce endometrial cancer risk
