Updated: 1/14/2019

Osteoporosis

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Overview
 

 
Snapshot
  • A 68-year-old woman presents to her primary care physician with lower back pain of acute onset. She denies any trauma to the spine or any radiation of pain. Her last menstrual period was when she was 51-years-old. On physical exam, she has tenderness to palpation at the level of L4-L5, as well as a loss of lumbar lordosis. A dual-energy x-ray absorptiometry (DEXA) scan reveals a T-score of -2.7.
Introduction
  • Clinical definition
    • decreased bone mass (osteopenia) that significantly increases the patient's risk of fracture
  • Epidemiology
    • incidence
      • most common types of osteoporosis are
        • post-menopausal
        • senile
    • risk factors 
      • post-menopausal women
      • being ≥ 65 years of age
      • people of Caucasian and Asian descent
      • lifestyle factors
        • poor physical activity
        • vitamin D deficiency and poor calcium intake
        • smoking
        • alcohol use disorder
      • medications
        • warfarin
        • lithium
        • proton pump inhibitors
        • glucocorticoids 
      • hyperparathyroidism
      • hyperthyroidism
      • multiple myeloma
      • malabsorption syndromes
      • low body weight 
        • higher body weight associated with higher bone density
  • Pathogenesis
    • in young adulthood, peak bone mass is achieved and this is determined by a number of factors (e.g., genetics)
      • after this peak bone mass is attained, there is a small decrease in bone formation with every cycle of bone remodeling
        • senile osteoporosis
          • osteoblasts have their biosynthetic and proliferative ability reduced with age
        • poor physical activity
          •  mechanical force on bone stimulates bone remodeling
            • athletes have increased bone density
          • decreased physical activity results in bone loss
        • decreased estrogen levels
          • such as in menopause, decreased estrogen levels increase bone resportion and formation
            • however, the rate of formation is less than resorption resulting in a net bone loss
            • increased osteoclast activity is significant in areas of bone with large surface area
              • such as the vertebral bodies, leading to vertebral compression fractures 
        • there is trabecular and cortical bone loss
  • Prognosis
    • generally good if detected early and appropriately managed
Presentation
  • Symptoms
    • fractures (e.g., vertberal and hip), otherwise, patients are typically asymptomatic
  • Physical exam
    • may see loss in height

Imaging

  • DEXA
    • indication
      • all women ≥ 65 and all men ≥ 70 years of age 
    • notes
      • T-score ≤ -2.5
Studies
  • Labs
    • serum calcium, phosphorus, parathyroid hormone, and alkaline phosphatase are normal
  • Histology
    • histologically normal; however, there is a decreased quantity of normal bone
Differential
 
Laboratory Abnormalities in Select Bone Disorders
Etiology
Serum Phosphate
Serum Calcium
Serum Alkaline Phosphatase
Parathyroid Hormone
Osteomalacia / rickets
  • Decreased
  • Decreased
  • Increased
  • Increased
Osteoporosis 
  • Normal
  • Normal
  • Normal
  • Normal
Osteopetrosis
  • Normal
  • Normal or decreased
  • Normal
  • Normal
Paget disease of the bone
  • Normal
  • Normal
  • Increased
  • Normal
Osteitis fibrosa cystica
  • Primary
    hyperparathyroidism
    • decreased
  • Secondary
    hyperparathyroidism
    • increased
  • Primary
    hyperparathyroidism
    • increased
  • Secondary
    hyperparathyroidism
    • decreased
  • Primary and secondary hyperparathyroidism
    • increased
  • Primary and secondary hyperparathyroidism
    • increased
Hypervitaminosis D
  • Increased
  • Increased
  • Normal
  • Decreased
 
Treatment
  • Conservative
    • calcium and vitamin D supplementation
    • strength training
    • smoking cessation
  • Medical
    • bisphosphonates
      • indication
        • first-line for pharmacologic therapy in osteoporosis
    • teriparatide
      • indication
        • considered first-line in patients with a very high risk of fracture
Complications
  • Fragility fractures
    • hip
    • distal radius
    • vertebral body
    • proximal humerus
 
 

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Questions (4)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
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(M1.MK.4666) A 72-year-old woman comes to you complaining of severe back pain. She reports that she slipped and fell in her shower at home. She also had a wrist fracture two years ago and an ankle fracture last year. The patient reports that she has been taking an over-the-counter vitamin D supplement. She has not had any diffuse bone pain. Figure A shows a radiograph of her spine. Which of the following is the most likely underlying abnormality? Review Topic

QID: 107095
FIGURES:
1

Subperiosteal bone resorption

31%

(9/29)

2

Vitamin D deficiency

0%

(0/29)

3

Excessive unmineralized osteoid

24%

(7/29)

4

Trabecular thinning

38%

(11/29)

5

Hypocalcemia

3%

(1/29)

M1

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