Osteoporosis Flashcards
Define osteoporosis.
Osteoporosis is a complex metabolic bone disease characterised by low bone density and micro-architectural defects in bone tissue, resulting in increased bone fragility and susceptibility to fracture
Normal ageing process with normal ratios and normal ALP.
What score defines osteoporosis?
T score of equal to or less than -2.5 = osteoporosis i.e. BMD result is equal to, or more then, 2.5 SDs below the young adult mean BMD
T score -1 to -2.5 = osteopenia i.e. The BMD result is between 1 and 2.5 SDs bellow the young adult mean BMD
What does DEXA stand for?
Dual X ray absorptiometry
?hip and lumbar spine
Define T score on DEXA.
SD from the mean of a young healthy population (useful to determine risk of #)
Define Z score on DEXA.
SD from mean of AGE-MATCHED control (useful to identify accelerated bone loss in younger patients)
What does DEXA stand for?
Dual X ray absorptiometry
?hip and lumbar spine
How does T score correlate with fracture risk?
For each standard deviation fall in BMD, there is an 1.5-3 fold increase risk of fracture
How does osteoporosis usually present?
Asymptomatic until fracture occurs - e.g. NOF, Colle’s.
Fall prevention is first-line therapy.
When is the Z score used?
Children, adolescents, young adults and adults before 50s
T score cannot be used in this population
Which bone is most important for DXA scanning in hyperparathyroidism?
Forearm
A 56 year old woman sustains a right wrist fracture after a fall. She has a T scores of -2.9 at the neck of femur. Which treatment is most appropriate?
Alendronic acid 70mgs once a week and vitamin D3 1000 units once a day - low threshold for post-menopausal women
A 68 year old woman has taken denosumab 60mgs every six months for five years. Her BMD has improved. You decide to stop treatment in order to reduce risks of longer term treatment. How should you advise your patient?
Start and continue alendronic acid or zoledronic acid afor 2 years after treatment
NB: Stopping denosumab can be associated with a ‘rebound’ increase in bone turnover, leading to rapid falls in bone density and vertebral fractures.
What type of bone is most bone made up of?
Cortical 90%
Trabecular 10%
What are the most common sites for osteoporotic fractures?
- Spine
- Neck of femur
- Forearm (Colle’s)
What are the 4 stages of normal bone remodelling?
- Resorption
- Reversal
- Formation
- Resting
What are the risk factors for osteoporosis?
Constitutional
- Female gender
- Age
- Asian or Caucasian
- Sex hormone deficiency
- Previous fragility fracture
- Family h/o fragility fracture
- Comorbidities
- Neuromuscular disorders
Lifestyle
- Low BMI
- Smoking
- Excessive alcohol
- Prolong immobilisation
- Low dietary calcium intake
- Vit D deficiency
List 5 modifiable risk factors for fracture.
- Low BMD
- Steroid use
- Low BMI
- Hypogonadism in men
- Smoking
- Excessive alcohol intake
- Poor diet/low Ca intake
- Vit D deficiency
- Long term immobilisation
What investigations would you do for osteoporosis?
DXA scan (dual-energy x-ray absorptiometry) - DIAGNOSTIC, much less radiation than CXR so safe.
- T score <-2.5 = osteoporosis
- T score <-2.5 with fragility fracture = severe osteoporosis
- T score -1 to -2.5 = osteopenia
X-ray - may show osteopenia and or fractures but is NOT DIAGNOSTIC.
Bloods to rule out cause:
- 25-hydroxyvitamin D levels of <20 nanograms/mL
- Testosterone deficiency
- TFTs - ?hyperthyroidism
- PTH - ?hyperparathyroidism
- Urinary free cortisol - high in Cushing’s
- Serum/urine protein electrophoresis - abnormal in myeloma
- Combination of low serum 25-hVitD, low serum/urine Ca, low serum phosphate and high PTH and AlkPhos = Vitamin D deficiency with or without osteomalacia.
How is osteoporosis managed?
Conservative:
- Weight bearing exercise
- Stop smoking
- Reduce EtOH
- Exclude secondary causes e.g. mets, MM, osteomalacia, Paget’s, endocrine (menopause, hyperthyroid)
Medical -
ALL PATIENTS ON CALCUM + COLECALCIFEROL
1st line: Bisphosphonates e.g. alendronate/risedronate PO - bone resorption reduced (morning on empty stomach). NB: check renal function, CI if eGFR <30ml/min → refer. Continue for 5yrs if well tolerated.
Other:
- Teriparatide SC (PTH derivative) - anabolic
- Raloxifene PO - SERM, used in post-menopausal women if alendronate CI
- Denosumab SC = for prevention and treatment; denosumab is a human monoclonal antibody to RANKL, a cytokine that is involved in mediating osteoclast activity.
- Strontium PO- anabolic + anti-resorptive
What is the recommended calcium and vitamin D3 dose daily?
calcium - 800-1000mgs daily
vitamin D3 - 1000 units daily
Which treatment is used where spinal T scores are very low?
Teriparatide = a peptide including the 34 amino acids of the N terminal part of parathyroid hormone. It is self-injected daily and is expensive so not first line.
What is the most effective intervention for osteporosis in anorexia nervosa?
Weight gain and resumption of periods is better than any other intervention (e.g. COCP, alendronic acid, calcium, vit D3)
What drugs for osteoporosis are contraindicated in very low eGFR?
- Alendronic acid
- Ibandronic acid
- Risedronate
- Zolendronic acid
These are all cleared via the kidneys. Denosumab is a monoclonal antibody and so could be used in the situation
What is important to check before calculating a FRAX score for a patient?
That the correct country has been selected - calculations vary by country
