Objectives: Previous studies have reported that the rise in parathyroid hormone (PTH) concentrations may be used to determine the levels of vitamin D adequacy. However, dietary calcium intake may also influence the rise in PTH. In the light of low calcium intakes in Indian adolescents, our aim was to investigate the relative importance of calcium intake in relationship of serum 25 hydroxyvitamin D (25OHD) with intact serum PTH in apparently healthy children.
Methods: A cross-sectional study on apparently healthy adolescents aged 1014 years (n=181), from Gujarat, Western India, was conducted from January 2012 to March 2014. Serum 25OHD concentrations (chemiluminescent microparticle immunoassay), serum PTH (chemiluminescent microparticle immunoassay) were measured. Diet was recorded through 24 h diet recall and calcium intake was computed (C-dietV2). To assess relationship between 25OHD and PTH, data were dichotomized according to median calcium intakes (520 mg) and relationship between serum 25OHD and PTH in the two subgroups were plotted.
Results: Mean levels of 25OHD, PTH and dietary calcium among study population were 17.7±6.8 ng/ml, 37.3±26.1 pg/ml and 570±262 mg /d respectively. Subjects with calcium intakes >520 mg had lower PTH for given vitamin D while those with calcium intake <520 mg had higher PTH values for given vitamin D. 25OHD was negatively correlated with serum PTH at lower as well as higher calcium intake, (r=−0.606 and −0.483 respectively, P<0.01 for both). The plot (Default 1) revealed existence of curvilinear inverse relationship between 25OHD and PTH; PTH vs 25OHD curve showed a negative shift with increasing calcium intake.
Conclusion: Dietary calcium intake influences relationship between 25OHD and PTH. Dietary calcium intake should be taken into account when assessing an individuals serum PTH level.
Disclosure: The authors declared no competing interests.
Figure 1 Shift of 25OHD vs PTH curve to left with increasing calcium intake.
27 - 30 Jun 2015