Laboratory Evaluation for a 32-Year-Old with Osteopenia
All young adults with osteopenia require comprehensive laboratory screening to identify secondary causes of bone loss, which are present in 44-90% of cases in this age group. 1
Essential Initial Laboratory Tests
The following tests have 92% sensitivity for detecting secondary causes of osteoporosis and should be obtained in all young adults with osteopenia 1:
- Serum calcium (corrected for albumin) 1
- Serum phosphate 1
- 25-hydroxyvitamin D level 1
- Parathyroid hormone (PTH) - only if calcium or urinary calcium is abnormal 1
- Serum alkaline phosphatase 1
- Complete blood count 1
- Serum creatinine 1
- Protein electrophoresis 1
- Testosterone level (in males) 1
Most Common Secondary Causes to Investigate
In Men <50 Years
The most frequent secondary causes account for 40-60% of cases 1:
- Hypogonadism (testosterone deficiency)
- Alcoholism
- Glucocorticoid exposure
In Premenopausal Women
The most common secondary causes account for 35-40% of cases 1:
- Estrogen deficiency (premature menopause, amenorrhea)
- Glucocorticoid exposure
Additional Risk Factors to Assess
Through history and physical examination, evaluate for 1:
- Low body weight (weight <70 kg is the single best predictor of low BMD) 2
- Tobacco use
- Excessive alcohol consumption
- Opiate abuse
- Malabsorption disorders (celiac disease, inflammatory bowel disease)
- Chronic inflammatory conditions
- Family history of osteoporosis or hip fracture
Clinical Context for Laboratory Interpretation
Vitamin D deficiency is extremely common, affecting 40-80% of certain populations, and must be corrected before considering bisphosphonate therapy 1. Severe vitamin D deficiency can cause osteomalacia, which presents with bone pain, muscle weakness, low calcium and phosphorus, elevated alkaline phosphatase, and elevated PTH 1.
Important caveat: Serum calcium and phosphate levels are often normal in secondary osteoporosis because calcium is mobilized from bone to maintain serum levels 1. Therefore, normal calcium does not exclude bone disease.
When PTH Testing Is Needed
PTH measurement is unnecessary unless you find 1:
- Abnormal serum calcium level
- Abnormal urinary calcium level
This targeted approach avoids unnecessary testing while maintaining diagnostic sensitivity.