Metabolic Bone Disease Flashcards
What are factors which stimulate osteoclast expression of RANK ligand?
PTH, glucocorticoids, vitamin D, IL-11…
Osteoblast produces small molecule - RANK ligand which activates osteoclast to be multinucleated and remove bone
How is Vitamin D absorbed?
Skin as 7DHC
Then in liver 25(OH)Vit D (not active)
Then metabolised in kidney 1,25(OH)2 Vit D
What is Paget’s disease of bone?
Localised disorder of bone turnover
Increased bone resorption followed by increased bone formation
Leads to disorganised bone - bigger, less compact, more vascular and more easily deformed or fractured
Describe the genetic component of Paget’s disease?
15-30% are familial
Loci of SQSTMI
Restricted geographical distribution
Environmental trigger - possibly chronic viral infection within osteoclast
What are the symptoms of Paget’s disease?
Presents in a patient over 40 years old with bone pain
Occasionally with bone deformity
Excessive heat over the Pagetic bone or neuro complications (nerve deafness)
What is the presentation of Paget’s disease?
Isolated elevation serum alkaline phosphatase
Bone pain and local heat
Bone deformity and fracture
Hearing loss
Rare development of osteosarcoma
What investigations are done for Paget’s disease?
X-ray and isotope bone scan
Paget’s disease does not cross a joint
What is the treatment of Paget’s disease?
Don’t treat asymptomatic unless in skull or in area of surgical intervention
Do not treat on raised alkaline phosphatase alone
IV Bisphosphonate therapy - one off IV zoledronic acid
What is the cause of Rickets and osteomalacia?
Severe nutritional vitamin D or calcium deficiency causes insufficient mineralisation
Muscle function also impaired in low vitamin D
Lack of vitamin D means less absorption of calcium and phosphate from gut so less available for bone mineralisation
What is the difference between Rickets and Osteomalacia?
Rickets is before the epiphyseal plate has fused
While osteomalacia is after - adult version
What is the blood results of Rickets and osteomalacia?
Low calcium, raised alkaline phosphatase, raised PTH and very low Vitamin D
What is the presentation of Rickets?
Small, fontanelles don’t close, skull looks bigger than it should, rickety rosery (lumps on ribs), lumps on epiphysis and bent legs
What is the presentation of osteomalacia?
Waddle gait
Muscle affected
Difficulty getting out of chair
Non-specific aching of bones
Can have micro-fractures on edges of bone - looser zones
How is rickets and osteomalacia treated?
Replace calcium and vitamin D - have to give lots
Sometimes if child has bowed legs then surgical intervention
What is osteogenesis imperfecta?
Genetic disorder of connective tissue characterised by fragile bones from mild trauma and even acts of daily life
Broad clinical range
What is the collagen defect in osteogenesis imperfecta?
Defects in type 1 collagen
Twenty eight different types genetically - first 4 are most common
What are signs and symptoms of osteogenesis imperfecta?
Growth deficiency, defective teeth formation, hearing loss, blue sclera, scoliosis, barrel chest, ligamentous laxity and easy bruising
Biggest problem is easy bone fractures
What is the management of OI?
Surgical to treat fractures
Medical to prevent fractures - IV bisphosphonates
Social - education and social
Genetic - genetic counselling
What is the definition of osteoporosis?
Metabolic bone disease characterised by low bone mass and micro-architectural deterioration of bone tissue - enhanced bone fragility and increase in fracture risk
How is osteoporosis diagnosed?
Result on DXA bone scanning <2.5
Thin bones
How is risk of osteoporosis measured?
FRAX - fracture risk assessment tool
Age, sex, BMI, fracture before, smoker, steroids, RA, alcohol and secondary osteoporosis
If more than 10% then refer to bone density assessment
What is Q fracture calculator?
Application for those aged 30-85, men and women
Contains variable including CV risks, falls and TCA
What is an DEXA?
Dual energy X-ray absorptiometry
Pictures of spine and hip, also lateral view
Computer generates bone mass
Less radiation than CT
Calculates T score (<2.5 is osteoporosis)
Who is at risk of osteoporosis?
1 in 2 women over 50 will have osteoporotic fracture
1 in 5 men over 50
50 year old women has 17% risk of hip fracture
If you suffer a vertebral fracture then more likely to have another
What are the endocrine cause of osteoporosis?
Thyrotoxicosis, hyper or hypoparathyroidism, cushing’s, hyperprolactinaemia, hypopituitarism and early menopause
What are rheumatic causes of osteoporosis?
RA, ankylosing spondylitis and polymyalgia rheumatica
What are gastroenterological causes of osteoporosis?
Inflammatory disease - UC and chrons
Liver disease - PBC, CAH, alcoholic cirrhosis and viral cirrhosis
Malabsorption - chronic pancreatitis, coeliac, whipples disease and short gut syndromes
What are medications which cause osteoporosis?
Steroids, PPI, enzyme inducting antiepileptic medications, aromatase inhibitors, GnRH inhibitors and warfarin
How do we prevent osteoporosis fractures?
Minimise risk factors
Ensure good calcium and vitamin D
Falls prevention strategies
Medications
What is the SIGN guidelines of osteoporosis treatment?
New emphasis on fracture risk assessment and fracture reduction
Treatment decisions after DXA scanning and individual report - if fracture score is 15% then would be at treatment threshold
What is the steroid guidance for osteoporosis?
If under age of 50 and on steroids - should have DXA scan
50-65 years - start oral bisphosphonate and DXA scan
Over 65 - oral bisphosphonate
What medications will help osteoporosis?
Antiresorptive therapies- HRT, SERMs, bisphosphonates and Denosumab
Anabolic therapies - Teriparatide and Romosuzumab
What is the side effects of HRT therapy?
Increased risks of blood clots
Increased risk of breast cancer with extended use into late 50/60s
Increased risk of heart disease and stroke if used after large gap from menopause
What are SERM medication?
Selective oestrogen receptor modulator
Reduces risk of vertebral fractures and no effect on non-vertebral fractures
Describe bisphosphonates
Generally fist line of treatment
Adequate renal function requires and calcium + vitamin D status
Good dental health and hygiene advised
What are the negative effects of SERMS?
Hot flushes if taken close to menopause
Increased clotting risk
Lack of protection at hip site
What is the mechanism of action of bisphosphonates?
Nitrogen containing inhibit osteoclasts
Interfere with mevalonic acid pathways - cholesterol metabolism
Reduce risk of vertebral and hip fractures
What are the side effects of bisphosphonates?
Oesophagitis
Iritis/ uveitis
Atypical femoral shaft fractures - rare
Drug holiday for 1-2 years
Osteonecrosis of jaw
Describe Denosumab
Monoclonal antibody against RANKL
Reduces osteoclastic bone resorption
Subcutaneous injection every 6 months
Safer in patients with significant renal impairment than bisphosphonates
What are the side effects of denosumab?
Allergy/ rash
Symptomatic hypocalcaemia if given when vitamin D deplete
Osteonecrosis of jaw and AFF
What is teriparatide?
PTH analogue
Single daily injection - stimulates bone to make bone given for 2 years
What are the side effects of Teriparatide?
Injection site irritation
Rarely hypercalcaemia
Allergy
Cost
What is Romosozumab?
Humanised monoclonal antibody inhibiting sclerostin
Increases bone formation and decreases bone reabsorption
Given by monthly sc injections
What are the side effects of Romo?
Allergy or serve skin reaction
If you have history of CVD then can cause heart attack or stroke
