What lab test is often elevated in osteoporosis?

Laboratory Tests in Osteoporosis

In osteoporosis itself, no specific lab test is characteristically elevated; however, bone turnover markers such as bone-specific alkaline phosphatase (BAP) and bone resorption markers (CTX, NTX) may be elevated when bone turnover is increased, though these are not used for diagnosis. 1

Understanding Laboratory Evaluation in Osteoporosis

The key concept is that osteoporosis is diagnosed by bone mineral density (BMD) measurement via DEXA scan, not by laboratory tests. 2, 3 Laboratory tests serve to identify secondary causes and assess bone metabolism, not to diagnose osteoporosis itself.

Bone Turnover Markers (Not Diagnostic)

When bone turnover is elevated, the following markers may be increased:

Bone Formation Markers

• Bone-specific alkaline phosphatase (BAP) can be elevated in high bone turnover states 1, 3
• Osteocalcin may be increased 1
• N-terminal and C-terminal pro-peptides of type I procollagen (P1NP, P1CP) can be elevated 1

Bone Resorption Markers

• C-terminal cross-linking telopeptides of type I collagen (CTX) - can be elevated in serum or urine 1, 4
• N-terminal cross-linking telopeptides (NTX) - can be elevated in serum or urine 1

Critical limitation: These markers have 15-40% variability and are not used clinically for diagnosing osteoporosis because they cannot be translated into patient-specific fracture risk estimates. 1 They are primarily used to monitor treatment response, not for diagnosis. 4, 5

Standard Laboratory Workup (To Identify Secondary Causes)

The following tests are typically normal in primary osteoporosis but are ordered to rule out secondary causes:

Basic Metabolic Panel

• Serum calcium and phosphate - typically normal in primary osteoporosis 2, 3
• Albumin or total protein - needed to correctly interpret calcium levels 2, 3
• Serum creatinine - to assess kidney function 2, 3
• Alkaline phosphatase (ALP) - may be elevated if increased bone turnover present 3

Vitamin D Status

• 25-hydroxyvitamin D level - often low (deficiency is common in osteoporosis patients) 2, 3

Tests for Secondary Causes

• Thyroid-stimulating hormone (TSH) - to rule out hyperthyroidism 2, 3
• Intact parathyroid hormone (iPTH) - to evaluate for hyperparathyroidism if calcium is abnormal 2, 3
• Sex hormone levels (testosterone, SHBG, LH, FSH in men; estradiol, LH, FSH in women with menstrual irregularities) - to identify hypogonadism 2, 3

Additional Tests Based on Clinical Suspicion

• ESR or CRP - if inflammatory conditions suspected 2, 3
• Liver function tests - to identify liver disease 2, 3
• Celiac disease screening - if malabsorption suspected 3

Common Pitfalls

Do not order bone turnover markers for diagnosis - they have high variability (15-40%), are affected by time of day, feeding status, menstrual cycle, and comorbid conditions, and cannot establish the diagnosis of osteoporosis. 1, 4 Their primary utility is in monitoring treatment response to bisphosphonates or anabolic agents. 4, 5

The diagnosis requires DEXA scan showing T-score ≤-2.5 or the presence of a fragility fracture, not laboratory testing. 2, 3, 6