Endocrine Abstracts

Background: Osteocalcin (OC) is a bone-specific protein produced primarily by osteoblasts during bone formation. The OC concentration is used to assess fracture risk and monitor treatment of osteoporosis and other disorders of bone metabolism. To adequately interpret the OC concentration, it is necessary to calculate reference ranges from a healthy reference population, adapted to a specific laboratory method.

Methods: We established a healthy reference population from the participants of the first follow-up of the Study of Health in Pomerania. Serum OC concentrations were measured from frozen aliquots with the IDS-iSYS N-Mid Osteocalcin assay on the IDS-iSYS Automated System (Immunodiagnostic Systems, Frankfurt am Main, Germany). The coefficients of variation were 6.98% at low, 6.44% at medium, and 5.44% at high levels of control material. The reference interval was defined as the central 95% range between the 2.5th and the 97.5th percentile. Age-specific reference intervals were calculated for men aged 25–80 years and for pre-menopausal women aged 25–54 years by means of quantile regression. As in post-menopausal women aged 50–80 years OC was not influenced by age, we calculated an age-independent reference interval.

Results: Median (1st–3rd quartile) OC concentrations were 15.4 ng/ml (12.0–19.5 ng/ml) in 1119 men, 14.4 ng/ml (11.3–18.5 ng/ml) in 545 pre-menopausal women, and 18.7 ng/ml (13.7–25.6 ng/ml) in 502 post-menopausal women. Median OC concentrations were highest in 25–29-year-old men and women, were stable during the middle ages, and rose again after 65 years of age in men, and at transition to post-menopause in women. We observed that subjects with type 2 diabetes, intake of oral contraceptives or hormone replacement therapy had lower OC concentrations than subjects without these conditions.

Conclusion: We present sex-specific reference intervals for the serum OC concentration over a broad range of age groups to assess bone metabolism.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This work was supported, however funding details unavailable.