No Associations of 25-Hydroxycholecalciferol and Parathyroid Hormone Concentrations with Calcaneal Bone Characteristics in Community-Dwelling Elderly Subjects: A Cross-Sectional Study.

OBJECTIVE: This study examined the associations of 25-hydroxycholecalciferol [25(OH)D3] and intact parathyroid hormone (iPTH) concentrations with bone status parameters in elderly subjects. DESIGN/
SETTING: Cross-sectional data based on the follow-up 2008 of the longitudinal study on nutrition and health status of senior citizens in Giessen, Germany. PARTICIPANTS: One hundred eighty-eight independently living subjects aged 66-96 years. MEASUREMENTS: Serum concentrations of 25(OH)D3, iPTH, N-terminal propeptide of type 1 collagen (P1NP) and activity of alkaline phosphatase (ALP) were assessed. Broadband ultrasound attenuation, speed of sound and stiffness index were determined by calcaneal quantitative ultrasound (QUS). Multiple linear regression analyses were performed to analyse associations of 25(OH)D3 and iPTH with bone status parameters.
RESULTS: Median (range) 25(OH)D3 and iPTH concentrations were 62.8 (29.9-106.7) nmol/L and 4.6 (1.3-21.0) pmol/L, respectively. Neither 25(OH)D3 nor iPTH was associated with calcaneal bone characteristics measured by QUS, whereas negative associations between 25(OH)D3 and bone formation markers (P1NP and ALP) were found. In a sub analysis, 25(OH)D3 was negatively associated with ALP only in subjects with iPTH concentrations > 4.59 pmol/L.
CONCLUSION: The present study provides no evidence for independent associations of 25(OH)D3 and iPTH with calcaneal bone characteristics in community-dwelling elderly subjects with 25(OH)D3 concentrations between 30 and 107 nmol/L. However, 25(OH)D3 interacts with bone formation markers, particularly in subjects with high iPTH concentrations.