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Toronto Notes 2019 Metabolic Bone Disease Metabolic Bone Disease
• see2010ClinicalPracticeGuidelinesfortheDiagnosisandManagementofOsteoporosisfordetails
Osteoporosis
Definition
• aconditioncharacterizedbydecreasedbonemassandmicroarchitecturaldeteriorationofbonetissue with a consequent increase in bone fragility and susceptibility to fracture
• bonemineraldensity(BMD)≥2.5standarddeviationsbelowthepeakbonemassforyoungadults(i.e. T-score ≤–2.5)
• osteopenia:BMDwithT-scorebetween–1.0and–2.5
ETIOLOGY AND PATHOPHYSIOLOGY
Primary Osteoporosis
• 95%ofosteoporosisinwomenand80%inmen
• post-menopausalwomen,duetodeclineinestrogen
Endocrinology E41
Corticosteroid Therapy is a Common Cause of Secondary Osteoporosis
Individuals receiving ≥7.5 mg of prednisone daily for over 3 mo should be assessed for bone-sparing therapy
Mechanism: increased resorption + decreased formation + increased urinary calcium loss + decreased intestinal calcium absorption + decreased sex steroid production
Calcium Plus Vitamin D Supplementation and Risk of Fractures. Osteoporosis
Int 2015;27:367-376
Purpose: To review trials of Vitamin D and Calcium therapy for reducing fracture risk in osteoporosis. Study: Systematic review searching 2011-2015, inclusive, identified 8 RCTs totalling 30,970 participants. RCTs reviewed included healthy adults and ambulatory older adults with medical conditions (excluding cancer). Vitamin D and Calcium combination therapy was compared to placebo. Results: Analysis of RCT data revealed that calcium plus vitamin D supplementation produced
a statistically significant reduction in risk of
total fractures (0.85; CI:0.73-0.98) and in hip fractures (0.70; CI:0.56-0.87). Subgroup analysis was significant for community dwelling or institutionalized patients.
Conclusions: Systematic analysis suggests
that Vitamin D and calcium therapy significantly decreases fracture risk. This study did not specifically look at individuals with osteoporosis. However, it still supports that Vitamin D and calcium should continue to be used as preventative treatment for individuals at increased risk of fractures.
Clinical Signs of Fractures or Osteoporosis
• Height loss >3 cm (Sn 92%) • Weight <51 kg
• Kyphosis (Sp 92%)
• Tooth count <20 (Sp 92%) • Grip strength
• Armspan-height difference >5 cm (Sp 76%)
• Wall-occiput distance >0 cm (Sp 87%) • Rib-pelvis distance ≤2 finger breadth (Sn
88%)
Secondary Osteoporosis
• gastrointestinaldiseases ■ gastrectomy
■ malabsorption (e.g. celiac disease)
■ chronic liver disease • bonemarrowdisorders
■ multiple myeloma ■ lymphoma
■ leukemia
• endocrinopathies
■ Cushing’s syndrome
■ hyperparathyroidism ■ hyperthyroidism
■ premature menopause ■ DM
■ hypogonadism
• malignancy
■ secondary to chemotherapy ■ myeloma
Clinical Features
• drugs
■ corticosteroid therapy
■ phenytoin
■ chronic heparin therapy
■ androgendeprivationtherapy ■ aromatase inhibitors
• other
■ rheumatologic disorders
◆ rheumatoid arthritis
◆ SLE
◆ ankylosing spondylitis
■ renal disease
■ poor nutrition ■ immobilization
• COPD (due to disease, tobacco, and glucocorticoiduse)
• commonlyasymptomatic
• heightlossduetocollapsedvertebrae
• fractures:mostcommonlyinhip,vertebrae,humerus,andwrist
■ fragility fractures: fracture with fall from standing height or less
■ Dowager’s hump: collapse fracture of vertebral bodies in mid-dorsal region
■ x-ray: vertebral compression and crush fractures, wedge fractures, “codfishing” sign (weakening of
subchondral plates and expansion of intervertebral discs) • pain,especiallybackache,associatedwithfractures
Approach to Osteoporosis
1. assess risk factors for osteoporosis on history and physical
2. decide if patient requires BMD testing with dual-energy x-ray absorptiometry (DEXA): men and
women ≥65 yr (or younger if presence of risk factors, see table 33, E42)
3. initial investigations
■ all patients with osteoporosis: calcium corrected for albumin, CBC, creatinine, ALP, TSH
■ also consider serum and urine protein electrophoresis if vertebral fractures, celiac workup, and 24 h
urinary Ca2+ excretion to rule out additional secondary causes
■ 25-OH-VitaminDlevelshouldonlybemeasuredafter3-4moofadequatesupplementationand
should not be repeated if an optimal level ≥75 nmol/L is achieved
■ lateral thoracic and lumbar x-ray if clinical evidence of vertebral fracture (or in individuals at moderate risk of fracture to help decide if they require medical therapy)
4. assess 10-yr fracture risk by combining BMD result and risk factors
1) WHO Fracture Risk Assessment Tool (FRAX)
2) Canadian Association of Radiologists and Osteoporosis Canada Risk Assessment Tool (CAROC)
◆ approach to management guided by 10-yr risk stratification into low, medium, high risk
5. for all patients being assessed for osteoporosis, encourage appropriate lifestyle changes (see Table 34,
E42)