calcium and osteoporosis Flashcards
role of Ca2+
changes excitability of cells, hypocalcaemia causes spasm and hypercalcaemia causes arrhythmias
cortical bone
outside of the bone, very dense, concentric osteocyte rings arranged around a central canal
bone turnover
- osteoclast recruits other OCs
- OCs dissolve bone and release IGF and TGF beta to attract OB precursors
- these mature to osteoblasts
- they fill the cavity and release RANKL
- this increases osteoclast differentiation and osteoprotegerin
what does parathyroid hormone do
releases Ca2+ from bone
- fast exchange: efflux of calcium from labile pool by binding to receptors on OCs and OBs causing cAMP increase
- slow exchange: PTH activates OBs to release RANKL to activate OCs
release of parathyroid hormone
parathyroid glands release PTH when plasma Ca2+ falls
release of calcitonin
C cells in thyroid glands when plasma Ca2+ increases
role of calcitonin
decrease plasma calcium, inhibits OB activity and Ca2+ resorption in the kidney
synthesis of vitamin D
synthesised in the skin by sunlight or taken in the diet
role of vitamin D
pre-hormone that once metabolised increases Ca2+ absorption in the GIT, acts at nuclear receptors
osteoporosis
metabolic bone disease characterised by a reduction in bone mass per unit volume that occurs with increasing age
T score
number of standard deviations by which the individuals bone mass density differs from the mean peak
T score results
normal - >-1
osteopenia - -1 - -2.5
osteoporosis - <-2.5
established osteoporosis - <2.5 & fracture
primary osteoporosis
age related
secondary osteoporosis
related to another medical conditions or drug induced
symptoms of osteoporosis
spinal collapse, height loss, pain, deformation, vertebrate, wrist NOF break
prognosis of osteoporosis
50% of patients with a hip fracture lose ability to live independently
after initial vertebrate fracture - 7 x increase of further fracture
management of osteoporosis
identifying and treating at risk patients
- low BMI/post menopausal/family history of maternal hip fracture <75y/o/alcohol/smoking
offer prophylaxis if needed
treatment for osteoporosis
- regular low impact exercise
- no smoking/alcohol
- 3-4 portions of calcium rich foods a day
- 400 units of vit D daily
- 1st line medication: bisphosphonates daily/weekly
- 2nd line: denosumab, raloxifene
- with calcium & vit d
how to take bisphosphonates
empty stomach 30-60 mins before food/medicine in the morning, with a full glass of water. report any mouth/oesophageal irritation
bisphosphonate warnings
osteonecrosis of jaw/ear - maintain good hygiene and report any pain or discharge
atypical femoral fractures - report any thigh, hip, groin pain
vitamin D deficiency
increased risk at serum 25-hydroxyvitamin d levels less than 25 nmol/l and are insufficient between 25-50 nmol/l
vitamin d deficiency treatment
colecalciferol (400 units = 10mcg) loading dose of 50/40 000 for 6/7 weeks or 4000 for 10
