Unit Converter
Osteocalcin (OCN)
Synonym
Bone gamma-carboxyglutamic acid-containing protein (BGLAP)
Units of measurement
ng/mL, ng/dL, ng/100mL, ng%, ng/L, µg/L
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OSTEOCALCIN (OCN)
(Bone Formation Marker - Reflects Osteoblast Activity, Bone Turnover, and Metabolic Bone Disorders)
Synonyms
- Osteocalcin (OCN)
- Bone γ-carboxyglutamic acid protein (BGP)
- Bone Gla protein
- OC
- Bone formation marker
Units of Measurement
- ng/mL
- ng/dL
- ng/100 mL
- ng%
- ng/L
- µg/L
Molecular Weight
~5.4 kDa
Unit Conversions
Direct Mass Conversions
1 ng/mL=1 µg/L1\ \text{ng/mL} = 1\ \text{µg/L}1 ng/mL=1 µg/L 1 ng/mL=100 ng/dL1\ \text{ng/mL} = 100\ \text{ng/dL}1 ng/mL=100 ng/dL 1 ng/mL=100 ng/100 mL1\ \text{ng/mL} = 100\ \text{ng/100 mL}1 ng/mL=100 ng/100 mL \text{ng%} = \text{ng/dL}
ng/L
1 ng/L=0.001 ng/mL1\ \text{ng/L} = 0.001\ \text{ng/mL}1 ng/L=0.001 ng/mL
Description
Osteocalcin is a non-collagenous protein secreted exclusively by osteoblasts, serving as one of the most important bone formation and turnover markers.
It is:
- Vitamin K–dependent (requires γ-carboxylation)
- Influenced by vitamin D
- Released during active bone formation
- Also released from bone matrix during bone resorption
Osteocalcin exists in two forms:
- Carboxylated osteocalcin (cOC) → incorporated into bone
- Undercarboxylated osteocalcin (ucOC) → circulates more, increases with vitamin K deficiency
Most commercial immunoassays measure total osteocalcin.
Physiological Role
Osteocalcin regulates:
- Bone mineralization
- Calcium binding in bone matrix
- Glucose metabolism (acts as a metabolic hormone in newer studies)
- Insulin secretion and sensitivity (emerging evidence)
Levels reflect osteoblast activity and general bone turnover rate.
Clinical Significance
HIGH Osteocalcin
1. High Bone Turnover States
- Postmenopausal osteoporosis
- Hyperparathyroidism (primary or secondary)
- Hyperthyroidism
- Paget disease of bone
- Renal osteodystrophy
- Healing fractures
- Acromegaly
2. Vitamin D Deficiency / Treatment Response
- Initially rises with vitamin D therapy
- High during active bone remodeling
3. Medications
- Teriparatide (PTH analog)
- Antiresorptive therapy early phase (transient rise)
4. Children & Adolescents
Natural elevation due to rapid bone growth.
5. Physical Activity
High-intensity exercise increases osteoblast activity → ↑OCN.
LOW Osteocalcin
1. Reduced Bone Formation
- Osteoporosis with low turnover
- Osteomalacia (severe vitamin D deficiency)
- Hypoparathyroidism
- Long-term glucocorticoid therapy
- Chronic kidney disease (advanced)
2. Vitamin K Deficiency
Reduces carboxylation, may lower measured levels depending on assay.
3. Aging
Bone formation declines → OCN decreases.
4. Diabetes Mellitus
Some studies show lower OCN in type 2 diabetes (reduced bone turnover).
Reference Intervals
(Tietz 8E + IOF + Mayo + ARUP)
(Values vary by sex, age, menopausal status, and assay used.)
Adult Men
- 14 – 42 ng/mL
Premenopausal Women
- 11 – 43 ng/mL
Postmenopausal Women
- 15 – 46 ng/mL
(Wider range due to high turnover)
Children & Adolescents
- Markedly higher (up to 150 ng/mL during growth spurts)
Low Bone Turnover Indicator
- < 10 ng/mL → suggests suppressed bone formation
Units Description
ng/mL / µg/L
Primary reporting unit.
ng/dL / ng%
Older clinical chemistry units.
ng/L
Used in some automated assays.
Diagnostic Uses
1. Bone Formation Marker
Monitors:
- Osteoporosis
- Osteopenia
- Metabolic bone diseases
2. Treatment Monitoring
- Antiresorptive therapy (bisphosphonates, denosumab)
- Anabolic therapy (teriparatide)
- Vitamin D therapy
- Hyperparathyroidism treatment
3. Pediatric Bone Disorders
Useful in:
- Growth disorders
- Rickets
- Pediatric osteoporosis
4. Endocrine Diseases
- Thyroid disorders
- Diabetes
- Acromegaly
5. CKD–Mineral Bone Disorder
Osteocalcin correlates with bone turnover in renal failure.
Analytical Notes
- Immunoassays vary: some measure intact OCN, others N-mid fragment
- Samples should be collected in the morning (diurnal variation)
- Short half-life (~5 minutes for intact OCN)
- Fasting recommended (recent food intake suppresses OCN)
- Hemolysis does not significantly interfere
Clinical Pearls
- Osteocalcin rises earliest among bone markers during anabolic therapy.
- Low osteocalcin suggests low-turnover osteoporosis, common in diabetics and elderly.
- ucOC fraction increases in vitamin K deficiency, even when total OCN is normal.
- Children have naturally high OCN due to bone growth - always interpret with age-adjusted values.
Interesting Fact
Osteocalcin is one of the very few bone proteins that behaves like a hormone, influencing insulin secretion, energy metabolism, and even male fertility (emerging research).
SEO Unit Converter Text
Osteocalcin converter — convert between ng/mL, ng/L, µg/L, and ng/dL. Includes reference ranges for premenopausal/postmenopausal women, treatment monitoring patterns, and bone turnover interpretation.
References
- Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - Bone Markers
- IOF (International Osteoporosis Foundation) - Bone Marker Standards
- Endocrine Society Osteoporosis & Metabolic Bone Guidelines
- Mayo Clinic Laboratories - Osteocalcin
- ARUP Consult - Bone Turnover Markers
- NIH / MedlinePlus - Osteocalcin Test