Abstract:
Context: It is unclear whether the relationship between 25-OHD and PTH is modulated by age or gender. Objective: To assess the 25-OHD-PTH relationship in 340 adolescents (10-17. years) and 443 elderly (65-85. years) of the same ethnic group, and living in the same sunny country. Assessments: Calcium intake was estimated. Serum calcium, phosphorus, 25-OHD and PTH were measured. Body fat was determined by DXA. Results: 25-OHD levels were lower in the elderly in the overall group (p 0.001) and within genders. 25-OHD levels were lower in females in the overall group and within age subgroups (p 0.05). PTH levels were higher in the elderly in the overall population and in both genders (p 0.001). There were no gender differences in PTH levels within age subgroups. For the same 25-OHD level, PTH levels were comparable across genders but were 1.5-2 folds higher in the elderly compared to adolescents (p 0.001). PTH correlated positively with age (p 0.001), body fat (p= 0.02), and negatively with calcium intake (p 0.001), and 25-OHD (p 0.001). The magnitude of the correlation with 25-OHD decreased after adjustment for age but not for gender. In multivariate analyses, age, 25-OHD and fat mass were independent predictors for PTH. In the elderly, after adjustment for serum creatinine, only 25-OHD and creatinine were independent predictors of PTH. Conclusion: The negative relationship between 25-OHD and PTH is modulated by age but not gender. Desirable 25-OHD levels derived from examining the 25-OHD-PTH relationship should therefore take into account the age of the population of interest. © 2010 Elsevier Inc.