Osteocalcin (OC; synonyms: bone γ-carboxylglutamic acid-containing protein; bone Gla-protein (BGP)) is a peptide hormone.
Osteocalcin is produced in bone by osteoblasts (bone-building cells) and in tooth by odontoblasts (dentin-forming cells) and binds to hydroxyapatite and calcium.
The synthesis of osteocalcin is regulated by 1,25-dihydroxy vitamin D (synonyms: calcitriol, 1α-25-OH-D3). However, osteocalcin can only perform its function in bone formation if it is carboxylated (introduction of a carboxy group into an organic compound) by vitamin K posttranslationally (changes in proteins that occur after translation). Thus, vitamin D and vitamin K complement each other in a synergistic manner in bone formation.
Osteocalcin is considered a marker of bone formation (new bone formation).
The process
Material needed
- 1 ml blood serum
- Blood collection in the morning between 08.00 and 09.00 (= physiological OC peak).
- Immediate forwarding of the sample to the laboratory or centrifuge within 2 hours, pipette serum (remove with the aid of a pipette) and freeze (approx. -20 °C).
Preparation of the patient
- Blood draw in the morning fasting
Interfering factors
- None known
Standard values
| Standard values in μg/l | |
| Women | |
| – premenopausal | 11-43 |
| – postmenopausal | 15-46 |
| Men | |
| <30 years | 24-70 |
| 30 – < 50 years | 14-42 |
| ≥ 50 years | 14-46 |
Indications
- Suspected osteoporosis (bone loss).
- Malignancies with bone metastases
- Primary hyperparathyroidism (parathyroid hyperfunction).
- Renal osteopathy – term for all skeletal symptoms and disorders of mineral metabolism associated with chronic renal insufficiency (process leading to a slowly progressive reduction in renal function).
Interpretation
Interpretation of increased values
- Increased bone remodeling with increased osteoblast activity.
- Primary and secondary hyperparathyroidism (parathyroid hyperfunction).
- Osteoporosis (high-turnover; high-turnover osteoporosis with rapid bone loss/fast-losing situation).
- Bone metastases in malignancies
- Osteomalacia (softening of the bones)
- Hyperthyroidism (hyperthyroidism)
- Paget’s disease (osteodystrophia deformans) – disease of the skeletal system with bone remodeling.
- Renal insufficiency (due toaccumulation of OC fragments).
Interpretation of decreased values (= decreased osteoblast activity).
- Hypoparathyroidism (parathyroid insufficiency).
- Osteoporosis (low-turnover; low-turnover osteoporosis with low bone resorption rate/slow-loss situation).
- Rheumatoid arthritis – chronic inflammatory multisystem disease, usually manifested in the form of synovitis (inflammation of the synovial membrane).
- Glucocorticoid therapy (→ glucocorticoid osteopathy/bone disease).
Further notes
- Higher values are measured in children with maximum during body growth.
- Postmenopausal frequent increase in osteocalcin in the context of progressive estrogen deficiency.
- In case of renal insufficiency (due toaccumulation of OC fragments), the determination of ostase is preferable because it has greater stability.
- False low values occur when stored unrefrigerated for too long due to loss of immunoreactivity.
