Osteocalcin (OC) or bone Gla protein (BGP), a bone specific protein, is one of circulating biomarkers that can be used to determine the quality of bone tissues. It is synthesized by the osteoblast and the odontocyte. The process of OC production requires two types of vitamin: vitamin D and vitamin K. Vitamin D is required for the production of immature OC or undercarboxylated OC (UcOC) whereas vitamin K is required for the transformation of UcOC to mature OC. In the past, several researchers believed that UcOC was the sensitive marker to determine vitamin K status. In fact, the level of UcOC also depends on vitamin D. This study aims to know the correlation between the levels of vitamin D and UcOC. The collected data of UcOC and vitamin D levels from 95 healthy volunteers were analyzed. The finding was that there was a weak correlation between UcOC and vitamin D (r = 0.238; p = 0.020) together with UcOC and reciprocal of vitamin D (r = 0.267; p = 0.009). From this correlation, the serum level of UcOC may be not the real marker for vitamin K.

Keywords: Undercarboxylated osteocalcin, Vitamin D, Vitamin K, Total vitamin D, 25 (OH) D