Metabolic Bone Disease Flashcards
Osteoclasts?
Breaks down bone and leaves a pit
Osteoblasts
Come and fill the pit with new bone- remodelling
How often is there complete remodelling of the skeleton?
Every 13 years
What is the main external factor which stimulates bone?
Vitamin D
Sources of vitamin D?
Sun, oily fish and egg yolk
Form of vitamin D absorbed into skin?
7DHC
How does skin melanin affect vitamin D absorption?
The more melanin, the harder to absorb adequate vitamin D
What happens to 7DHC when it goes to the liver?
Hydrolysed into 25(OH)vit D
What is the storage form of vitamin D?
25(OH) Vit D
Where is vitamin D?
Fat and muscle of liver
What happens when we need to vitamin D physiologically?
Vitamin D hydrolysed by kidney into 1,25 (OH)2 Vit D (active form)
Function of calcium?
Maintain extracellular calcium within tight limits
->allows for heart to pump and nerves to conduct
How are phosphate and
calcium absorbed with the help of vitamin D?
If enough in the diet, absorbed from the gut.
If not enough, calcium and phosphate are absorbed from the bone
Which hormone helps to get calcium from bone?
Parathyroid hormone
Paget’s disease?
Increased bone resorption followed by increased bone formation
What result does Paget’s disease have on bone?
Disorganised bone; bigger, less compact, more vascular and more susceptible to deformity and fracture
Predisposition to Paget’s disease?
Strong genetic component but with an environmental trigger e.g. possible chronic viral infection
Paget’s disease only occurs over the age of?
40
->will not be diagnosed in someone younger
Symptoms of Paget’s disease?
Bone pain
Excessive heat over Paget bone
Nerve associated deafness
Investigation for diagnosis?
Isotope bone scan
->does not usually need to go on to a bone biopsy
What is important to note about Paget’s disease and joints?
Does not cross joints
What will be seen in bloods in someone with Paget’s?
Raised ALP
->do not treat based on raised ALP along, need symptoms too unless in skull
Treatment of Paget’s disease?
Only if symptomatic or affecting skull
IV bisphophonate therapy- one off
IV zoledronic acid
What causes rickets and osteomalacia?
Severe vitamin D or calcium deficiency causing soft bone
Can be due to diet deficiency or malabsorption
What is the difference between rickets and osteomalacia?
Rickets- occurs before growth plates fuse
Osteomalacia- occurs after growth plates fuse
As well as bone, what is affected by low vitamin D?
Muscle function
Bloods tests in rickets and osteomalacia?
Low calcium
Raised ALP
Raised PTH- trying to get calcium out of bone
Very low vitamin D
Abnormalities seen in a patient with rickets?
Fontanelles do not close
Lumps on rib cage
Barrel chest
Wide joints at wrist and elbow
Treatment for rickets?
Calcium and vitamin D supplements
-Ricket’s is very rare in the UK and can be a sign of severe child abuse
Who tends to get osteomalacia?
Elderly
Living in care home with little sun
Middle aged Asian women, more likely to stay at home or cover their skin
Symptoms of osetomalacia?
Bone pain
Muscle aches
What is commonest genetic disorder affecting bone?
Osteogenesis Imperfecta
Osteogenesis Imperfecta?
Genetic disorder of CT characterised by fragile bones from mild trauma or even acts of daily life e.g. picking up school bag
Signs and symptoms of Osteogenesis Imperfecta?
Growth deficiency
Defective tooth formation
Hearing loss
Blue sclera
Scoliosis
Barrel chest
Ligamentous laxity
Easy bruising
When is the only other time you might see blue sclera?
Marfans’ syndrome
Describe the management of osteogenesis imperfecta.
Surgical- to treat fractures
Medical- to prevent fracture e.g. IV bisphoshonates
Social- eduction adaptations
Genetic- genetic counselling for parents and next generation
What is osteoporosis?
Metabolic bone disease characterised by low bone mass
What does osteoporosis increase risks of?
Fractures
How can osteoporosis be diagnosed?
Bone density scans
Bone biopsy- all bone features thinner
When do people reach peak bone mass?
Age of 25
In women, when is there accelerated loss of bone density?
Menopause
->this is why osteoporosis is more common in women than men
What is used to assess who is at risk of fractures?
FRAX assessment tool
Q fracture
->used in clinical practice
If risks of fractures in the next ten years, what scan is done?
DXA scan
->measures level of bone mineral density
Who is at risk of osteoporosis?
> 50yrs (women specifically)
Women>men
Previous fractures increase risks of another
Endocrine causes of osetoporisis?
Thyrotoxicosis
Hyper and hypoparathyroidism
Cushings
Hyperprolactinaemia
Hypopituitarism
Early menopause
Rheumatic causes of osteoporosis?
Rheumatoid arthritis
Ankylosing spondylitis
Polymyalgia rheumatica
GI casuses of osteoporosis?
IBD
Liver disease
Malabsorption e.g. chronic pancreatitis, coeliac disease, ischaemic bowel
Medications which can cause osteoporosis?
Oral steroids
PPI
Enzyme inducing anti-epileptic meds
Aromatase inhibitors- used to breast cancer
GnRH inhibitors- used in prostate cancer
Warfarin
Management of osteoporosis?
Minimise risk factors
Ensure good calcium and vitamin D
Fall prevention strategies
Medications- previous management options more important for meds to work
Hehe lecturer said chocolate is a good source of calcium
And that you don’t need to be healthy to get good calcium intake
->and I am a women so need to reduce my risks as much as possible hehe
How should you manage patients on long-term steroids to reduce risks of osteoporosis?
Early bone density scan
If >65, DXA scan not necessary, just treat for osteoporosis
What are the two categories of bone meds?
Antiresorptive therapies- reduce bone breakdown
Anabolic therapies- those that rebuild bone
Give some examples of antiresorptive therapies which help to reduce the breakdown of bone.
HRT
SERMs
Bisphophonates
Denosumab
Give some examples of anabolic therapies which help to build bone up.
Teriparatide
Romosuzumab
Pros and cons of HRT?
Reduces risks of all fractures
Increased risks of blood clots
Increased risk of breast cancer with extended use into late 50s/early 60s
Increased risks of heart disease if used after a large gap after menopause
Side effects of SERMS?
Hot flushes
Increased risk of blood clots
Lack of protection at hip site
SERMS reduces risks of fracture rates EXCPET for?
Vertebral fratures
What is generally the first line osteoporosis medication after non-medical management?
Oral bisphosphonates
->reduce fracture risks without cancer risks
Side effects of bisphosphonates?
Oesophagitis
Uveitis/iritis
Atypical femoral shaft fracture*
ONJ (osteonecrosis of jaw)*
->those on bisphosphonates need to has a break for 1-2 years after being on for ten years to reduce the risks of the tow conditions with *
How is Denosumab taken?
Subcutaneous injection every 6 months
Which med can be given for osteoporosis in those with renal disease?
Denosumab
Side effects of denosumab?
Symptomatic hypocalcaemia if given when vitamin D depleet
ONJ- osteonecrosis of jaw
Atypical femoral shaft fractures
Teriparatide is an anabolic therapy.
Pros ad cons?
Very effective- greatly reduces fracture risks
Expensive so only given to severe cases
Side effects of Teriparatide?
Injection site irritation
Hypercalcaemia- rarely
Romosozumab is another anabolic therapy.
Pros and cons?
Monthly injection compared to daily of teriparatide
Higher risk of allergy
