Abstract
ObjectiveTo assess if serum free 25-hydroxyvitamin D (25OHD) is a better indicator of vitamin D status than total 25OHD in healthy children.MethodsCross-sectional prospective clinical study was designed. We measured serum free 25OHD concentrations and its correlation with calculated free 25OHD, total 25OHD, intact parathyroid hormone (PTH), and vitamin D binding protein (DBP) in children. The influence of age, sex, ethnicity, body mass index (BMI), season of the year, diet intake, vitamin supplements, time spent outdoors and albumin concentrations on free 25OHD was also analyzed. 241 children aged from 0 days to 14 years, and living in the northern Spain (latitude 43° N), were included.ResultsMean (SD) free 25OHD concentrations were 2.48 (1.39), 5.46 (3.12), 4.12 (1,72), 3.82 (1.43) pg/ml in children aged 0 days, 1 month-2 years, 2–6 years and >6 years, respectively. Correlation between directly measured and calculated free 25OHD was high and significant (r = 0.66) as well as the correlation between serum free and total 25OHD concentrations (r = 0.61). No significant correlation was found between PTH and free 25OHD (r = -0.08). The total 25OHD and PTH concentrations’ correlation was inverse (r = -0.25) and significant. Neither free nor total 25OHD concentrations correlated with DBP concentrations. Among the analyzed variables, free 25OHD values were higher in spring/summer than in autumn/winter in children older than 6 years.Conclusions: These findings do not support that free 25OHD is a better marker of vitamin D deficiency than total 25OHD in healthy pediatric population.
Highlights
The status of vitamin D is clinically estimated by measuring total serum 25-hydroxyvitamin D (25OHD)
No significant correlation was found between parathyroid hormone (PTH) and free 25OHD (r = -0.08)
Neither free nor total 25OHD concentrations correlated with D binding protein (DBP) concentrations
Summary
The status of vitamin D is clinically estimated by measuring total serum 25-hydroxyvitamin D (25OHD). Vitamin D plays a key role in the regulation of mineral metabolism [1], but in recent years a growing number of clinical studies have claimed an association between low vitamin 25OHD concentrations and increased susceptibility to certain acute and chronic diseases [2,3,4]. This potential role of vitamin D has prompted an increasing interest in detecting vitamin D deficiency. The normal values of DBP concentrations vary with age [9]
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