Bone physiology Flashcards
True or False
One vertebral fracture will lead to another
True
What do osteoclasts do?
Resorb bone
What do osteoblasts do?
Put down osteoid to form new bone
Who should be assessed using the risk factor assessment? (2)
Anyone over 50 with risk factors
Anyone under 50 with an early menopause or on steroids
When should a DEXA scan be requested?
10 year risk assessment of at least 10%
In a DEXA scan, which value is the most important?
T value
What does the T value have to be to be classified as osteoporosis?
More than -2.5
What is a Z score?
Age matched so compares with age and size
When are Z scores used?
If younger than 20
What class of drug is given if osteoporosis is diagnosed?
Bisphosphonate
What are examples of bisphosphonates?
Alendronic or risedronic acid
When is zolendronic acid given?
If DEXA intolerable
What is given in severe spinal osteoporosis?
Teriparatide
If osteopenia is diagnosed what is done?
Lifestyle advice e.g. smoking, alcohol, weight bearing exercise, falls advice
DEXA reassessment
True or False
Post-menopausal women should increase their dairy intake
True
How do bisphosphonates work?
Apoptosis of osteoclasts so inhibit bone resorption
What are long term potential side effects of bisphosphonates?
Osteonecrosis of jaw
Oesophageal Ca
How is zolendronic acid given?
Once yearly IV infusion
When is denosumab given?
If bisphosphonates intolerable.
How should alendeonic acid be given?
Tablet, 30 minutes before food and don’t lie down for half an hour after
When should alendronic acid be stopped?
Oesophagitis or ulcers
What are common side effects of alendronic acid?
Abdo pain
Nausea
dyspepsia
GI side effects
How does denosomuab work?
Monoclonal Ab that binds to RANKL
What is RANKL?
Receptor activator of nuclear factor kB ligand
How does activating RANKL prevent osteoporosis?
Inhibits osteoclasts and decreases bone resorption
How is denosomuab given?
Subcut injection 6 monthly
Why is strontium not recommended as 1st line?
Fracture reduction is slightly less and dangerous in heart disease
Where does Paget’s disease affect?
Long bones
Pelvis
Lumbar spine
Skull
What is Paget’s disease?
Increased osteoclast activity with abnormalities. Reduced strength
What is a complication of Paget’s disease?
Osteosarcoma
What symptoms may present with Paget’s?
Often asymptomatic but bone pain or deformity and deafness
How is Paget’s diagnosed?
XR
Increased alk phos
How is Paget’s treated?
Bisphosphonates
Which defect causes osteogenesis imperfecta?
COL1A1/2
Autosomal dominant
What is associated with osteogenesis imperfecta?
Blue sclerae
Dentinogenesis imperfecta
Which receptor on the parathyroid is for calcium?
Ca sensitive receptor
What kind of receptor is CaSR?
G protein coupled
How is vitamin D stored in the liver?
Cholecaliferol
What does the liver convert it to?
25-hydroxycholecaliferol
What does the kidney turn it into?
1,25-hydroxycholecaliferol
What are symptoms of acute hypercalcaemia?
Thirst
Dehydration
Polyuria
Confusion
What are symptoms of chronic hypercalcaemia?
Myopathy
Fractures
Depression
Abdo pain
What are major causes of hypercalcaemia?
Primary hyperparathyroidism
Malignancy
What drugs can cause hypercalcaemia?
Vitamin D
thiazides
What will blood results be for 1o hyperparathyroidism?
Raised serum Ca
Raised serum PTH
Increased urine Ca excretion
What other serum protein is important for diagnosing malignancy?
Alkaline phosphate (raised in malignancy)
What is the treatment for acute hypercalcaemia?
Fluids
Loop diuretics once rehydrated
Bisphosphonates will lower Ca
How is 1o primary hyperparathyroidism managed?
Surgery or nothing
When should surgery for 1o hyperparathyroidism be indicated?
If end organ damage e.g. renal stones, osteoporosis, gastric ulcers or renal disease
Or if calcium is v high (>2.85)
What is 2o hyperparathryoidism?
Physiological response to low Ca
PTH raised
What is 3o hyperparathyroidism?
Overactive PTH after many years of 2o
Which genetic syndromes are closely linked with hyperparathyroidism?
MEN1/2
What is FHH?
Familial hypocalciuric hypocalcaemia
What signs will be present in FHH?
Low Ca urine
Hypercalcaemia
How does PTH work on the gut?
Causes it to absorb Ca and therefore increased serum Ca levels
In which fish is vitamin D high in?
Herring
What are the symptoms of hypocalcaemia?
Paraesthesia in extremities and perioral
tetany and cramps
Fatigue and myopathy
Long QT on ECG
What are the causes of hypocalcaemia?
Hypoparathyroidism
Vitamin D deficiency
renal failure
Pancreatitis
What is the treatment for acute hypocalcaemia?
10ml 10% IV calcium gluconate over 10 mins
In what congenital condition is the parathyroid gland underachieve?
DiGeorge syndrome
What are the other features of DiGeorge syndrome?
Cardiac abnormalities Abnormal facies Thymus aplasia Cleft palate Hypoparathyroidism/hypocalcaemia Chromosome 22
What is the long term management of hypoparathyroidism?
Calcium supplement daily
Vitamin D tablet
Why can hypomagnaeseamia cause low calcium?
Ca release is Mg+ dependent
What causes hypomagnaeaemia ?
Alcohol
Thiazides
PPI
What is pseudohypoparathyroidism?
Genetic defect of GNAS1 which means that PTH is resisted
What are symptoms of pseudohypoparathyroidism?
Obesity
Learning disabilities
Brachdactyly of 4th metacarpal
Hypocalcaemia
What is pseudo-pseudohypoparathyroidism?
Same but with normal Ca
What can cause rickets?
Coeliac disease
Liver disease
Chronic renal failure
True or False
Alk phos is raised in Osteomalacia
True
