The relative influence of serum ionized calcium and 25-hydroxyvitamin D in regulating PTH secretion in healthy subjects

Document Type


Publication Date


Publication Title



BACKGROUND: While the inverse relationship between serum ionized calcium (Ca(2+)) and PTH is well-established, the relationship between 25(OH)D and PTH showed conflicting results. The study aimed to evaluate the relative contributions of age, sex, serum Ca(2+), ionized magnesium (Mg(2+)), 25(OH)D and 1,25(OH)2D in regulating PTH secretion in healthy subjects. METHODS: This is a secondary analysis of an observational study performed from March 2014 to July 2015 carried out in 2259 blood donors (1652 men and 607 women, age range 18-68years). Subjects with parathyroid disorders and taking drugs that affect mineral metabolism were excluded. RESULTS: Significant correlations [between Ca(2+) and PTH (r=-0.223, p<0.001), 25(OH)D and PTH (r=-0.178, p<0.001) and between PTH and age (r=0.322, p<0.001)] were found. As a preliminary step to multivariate analysis, a regression tree analysis was performed using PTH as response variable and age, Ca(2+), Mg(2+), 25(OH)D, 1,25(OH)2D and sex as explanatory variables to determine the effect of each covariate on the response variable. For subjects <38years, 25(OH)D was the most important parameter in regulating PTH. For subjects >/=38 both 25(OH)D and Ca(2+) levels regulated PTH secretion. Subjects with 25(OH)D<13ng/mL had average higher PTH; in this group only, subjects with Ca(2+)>/=1.30mmol/L had average lower PTH compared to subjects with Ca(2+)<1.30. The multivariate analysis showed that all variables had a significant effect (p<0.001) on PTH. Anova Type III errors c indicated that 25(OH)D accounted for 32.1% of the total variance in PTH, Ca(2+) accounted for 18% of the total variance, BMI for 14.3%, and 1,25(OH)2D for 11.1%. The remaining percentage was attributable to age and sex. This was confirmed by the regression tree approach, where 25(OH)D and Ca(2+) accounted for the largest variation in the average levels of PTH. DISCUSSION: Under stable conditions 25(OH)D plays a significant role in regulating PTH secretion. Under conditions of relative vitamin D sufficiency, Ca(2+) also plays an important role.

PubMed ID




First Page


Last Page