13) Endocrine & metabolic bone disorders Flashcards
(23 cards)
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
How do bisphosphonates work?
Taken up by osteocytes when they resorb bone + their function is impaired
What is Pagets disease a disease of?
Disorganised bone remodelling
What type of bone does Paget’s disease lead do?
Woven
Who does Pagets commonly effect?
Elderly
Which bones are most commonly effected in Paget’s?
Spine
Skull
Pelvis
Tibia
Pagets is P…..
painful
How is Paget’s disease bichemically diagnosed?
High alkaline phosphatase
How is Paget’s treated?
Bisphosphanates
