Objectives: Diabetes can affect bone via obesity, 
hyperglycemia, hyperinsulinemia, and hypoinsulinemia. 
Osteocalcin (OC) is a non-collagenous protein of the bone 
that contributes to bone formation. A population-based 
study was done to examine the relationship between the 
serum level of under carboxylated osteocalcin (ucOC) and 
diabetes.  
Methods: A cross-sectional study was done in 2,062 
women aged 40 to 69 years living in a suburban Japanese 
town. Serum ucOC level by electro chemiluminescent 
immunoassay, Fasting Plasma Glucose (FPG), and 
glycohemoglobin A1c (HbA1c) were measured for each 
participant. Participants who were previously diagnosed 
with diabetes or who were receiving its treatment were 
defined as having pre-existing diabetes. Participants without 
pre-existing diabetes who had a FPG level >7.0 mmol/L or 
HbA1c level of ≥6.5 % were defined as having newly 
diagnosed diabetes.  
Results: The median serum ucOC level of 1,433 
postmenopausal women (5.2 ng/mL) was significantly 
higher than that of 629 premenopausal women (3.1 ng/mL) 
(P<0.0001). The distribution of postmenopausal women   with pre-existing diabetes, newly diagnosed diabetes, and  
non-diabetes was 38 (2.7%), 88 (6.1%), and 1,307 (91.2%), 
respectively. The median serum ucOC levels of the 3
groups of postmenopausal women significantly decreased 
with worsened glucose metabolism (pre-existing diabetes 
3.38, newly diagnosed diabetes 4.51, and non-diabetes 5.51 
ng/mL) (P<0.0001). Multivariate regression analysis 
showed the FPG and HbA1c values to be negative factors 
independently associated with the serum ucOC level of 
postmenopausal women.  
Conclusions: These findings indicate that the serum ucOC 
levels decrease in postmenopausal diabetic women, 
suggesting a relationship between diabetes and 
osteoporosis.