Bone turnover markers in serum but not in saliva correlate with bone mineral density

Abstract

Saliva was proposed as a diagnostic tool for systemic diseases. Here we determined the correlation of bone turnover markers in saliva, bone turnover markers in serum and bone mineral density in postmenopausal osteoporotic and healthy women. Forty postmenopausal osteoporotic and 40 age-matched healthy non-osteoporotic females were recruited for this case-control study. Serum and stimulated saliva levels of osteocalcin, N-terminal propeptide of type I collagen, bone-specific alkaline phosphatase and cross-linked-C-telopeptide of type I collagen were determined. Bone mineral density of the lumbar spine, proximal femur, and total hip were obtained. We show that osteocalcin and cross-linked-C-telopeptide of type I collagen (CTX) reached detectable levels in saliva while N-terminal propeptide of type I collagen and alkaline phosphatase were close or below the detection limit. Serum levels of bone turnover markers were significantly higher than saliva levels. Correlation analysis revealed a strong correlation of serum osteocalcin and, to a lesser extent, also serum CTX values with bone mineral density in lumbar spine, femoral neck, or total hip, respectively. There was, however, no significant correlation of bone mineral density with the respective bone turnover markers in saliva. There was a trend that saliva osteocalcin correlates with femoral neck (p = 0.16) or total hip (p = 0.06). There was also no association between serum and saliva bone turnover markers. This study reveals that saliva cannot replace the withdrawal of serum to evaluate bone metabolism.

Figure 1

Overview of bone mineral density and bone turnover markers in serum and saliva. The data represent 40 postmenopausal osteoporotic women and 40 healthy non-osteoporotic females with bone mineral density (BMD) measured in the lumbar spine (Spine), femoral neck (Neck), or total hip (Total) expressed as T-score (A) and bone turnover markers osteocalcin (OC ng/ml) and cross-linked-C-telopeptide of type I collagen (CTX ng/ml) measured in serum (B) and saliva (C).

Figure 2

Correlations of bone turnover markers determined in saliva and serum with bone mineral density. The data represent 40 postmenopausal osteoporotic women and 40 healthy non-osteoporotic females with bone mineral density (BMD) measured in the lumbar spine expressed as T-score and bone turnover markers osteocalcin (OC) and cross-linked-C-telopeptide of type I collagen (CTX) measured in serum (A) and saliva (B). The p values are from Linear regression analysis.

Figure 3

Correlations of osteocalcin determined in saliva with total hip and femoral neck bone mineral density. The data represent 76 data points with bone mineral density (BMD) measured in the (A) total hip and (B) femoral neck expressed as T-score and bone turnover markers osteocalcin (OC) in saliva. The p values are from Linear regression analysis.

Figure 4

Correlation of bone turnover markers in serum and saliva. The data represent 76 data points from postmenopausal osteoporotic and healthy non-osteoporotic females with bone turnover markers (A) osteocalcin (ng/ml) and (B) cross-linked-C-telopeptide of type I collagen (CTX ng/ml) measured in the serum and in saliva. The p values are from Linear regression analysis.