What laboratory workup is recommended for patients with osteoporosis?

Laboratory Workup for Osteoporosis

The recommended laboratory workup for patients with osteoporosis should include serum calcium, phosphate, 25-hydroxyvitamin D, thyroid function tests, complete blood count, comprehensive metabolic panel, and tests to exclude secondary causes of osteoporosis. 1, 2

Basic Laboratory Tests

• Serum calcium and phosphate to assess bone metabolism and identify abnormalities 1
• 25-hydroxyvitamin D level to identify vitamin D deficiency, which is common in osteoporosis 1
• Albumin or total protein to correctly interpret calcium levels 1
• Serum creatinine to assess kidney function 1
• Complete blood count to screen for underlying hematologic disorders 2
• Comprehensive metabolic panel to evaluate liver and kidney function 2

Tests to Identify Secondary Causes

• Thyroid function tests (TSH) to rule out hyperthyroidism 1, 2
• Intact parathyroid hormone (iPTH) to evaluate for hyperparathyroidism 1
• Sex hormone levels:
  • In men: Serum testosterone, SHBG, LH, FSH to identify hypogonadism (accounts for 40-60% of male osteoporosis cases) 1, 2
  • In women: Estradiol, LH, FSH (particularly in premenopausal women with irregular menses) 1, 2
• Bone turnover markers (optional):
  • Serum procollagen type I N propeptide (s-PINP) for bone formation 1
  • Serum C-terminal telopeptide of type I collagen (s-CTX) for bone resorption 1
• Alkaline phosphatase (bone-specific) to assess bone formation 1

Additional Tests Based on Clinical Suspicion

• Erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) if inflammatory conditions are suspected 1
• Liver function tests (GOT, GPT, gamma-GT) to identify liver disease 1
• Fasting glucose and HbA1c to screen for diabetes 1
• Growth hormone (GH) and insulin-like growth factor 1 (IGF-1) if growth hormone deficiency is suspected 1
• Celiac disease screening (anti-endomysial, anti-transglutaminase antibodies) if malabsorption is suspected 1, 3
• 24-hour urinary calcium (optional) to assess calcium excretion 1

Diagnostic Imaging

• Dual-energy X-ray absorptiometry (DEXA) of lumbar spine and femoral neck is the gold standard for diagnosis 1
• Lateral X-rays of thoracic and lumbar spine to identify vertebral fractures, which may be asymptomatic 1

Considerations for Special Populations

• For patients with chronic liver disease, laboratory measurements should identify abnormal calcium and vitamin D metabolism 1
• For cancer survivors, more comprehensive testing may be needed, including evaluation of bone turnover markers 1

Clinical Pearls and Pitfalls

• Comprehensive testing can identify secondary causes of osteoporosis with 92% sensitivity 2
• Secondary causes of osteoporosis are present in 44-90% of patients with low bone mineral density 2
• Laboratory abnormalities may guide treatment decisions and identify correctable causes of bone loss 4, 3
• Undecalcified transiliac bone biopsy is rarely needed and recommended only in exceptional cases with presumed osteomalacia 1

Remember that identifying and addressing secondary causes of osteoporosis is crucial for effective management and can significantly improve treatment outcomes 2, 4.