Open AccessTotal, bioavailable and free 25-hydroxyvitamin D levels as functional indicators for bone parameters in healthy children
Author(s) -
You Joung Heo,
Yun Jeong Lee,
Kyung-Hoon Lee,
Jae Hyun Kim,
Choong Ho Shin,
Young Ah Lee,
Jae-Joon Song
Publication year - 2021
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0258585
Subject(s) - vitamin d and neurology , bone mineral , parathyroid hormone , medicine , bone remodeling , endocrinology , bone density , chemistry , biology , osteoporosis , calcium
Objectives Vitamin D is essential for bone health. Not only total but also free 25-hydroxyvitamin D (25OHD) may contribute to bone mass. We sought to determine which vitamin D measure best reflected clinical and bone parameters in healthy children. Methods A cross-sectional study including 146 healthy children (71 boys, 9.5 ± 1.9 years) conducted at a tertiary medical center. We used a multiplex liquid chromatography-tandem mass spectrometry-based assay to simultaneously measure vitamin D metabolites. The bioavailable and free 25OHD (25OHD BioA and 25OHD Free ) levels were calculated using the genotype-specific or genotype-constant affinity coefficients of vitamin D-binding proteins (yielding spe-25OHD BioA , spe-25OHD Free and con-25OHD BioA , con-25OHD Free respectively). The 25OHD Free level was directly measured (m-25OHD Free ). Bone mineral content (BMC) and bone mineral density (BMD) were assessed via dual-energy X-ray absorptiometry. Results The total 25OHD (25OHD Total ), the two forms of 25OHD BioA , the three forms of 25OHD Free , and 24,25-dihydroxyvitamin D 3 levels correlated with parathyroid hormone level (all p < 0.01). Serum 25OHD Total and m-25OHD Free levels were influenced by age, pubertal status, season, body mass index (BMI), daylight hours, and vitamin D intake (all p < 0.05). The con-25OHD BioA and con-25OHD Free levels better reflected pubertal status and daylight hours than did the spe-25OHD BioA and spe-25OHD Free levels (both p < 0.01). The association between the 25OHD Total level and bone parameters varied according to the BMI (interaction p < 0.05). In 109 normal-weight children, the con-25OHD BioA and con-25OHD Free levels correlated with total body BMC and BMD (both p < 0.05), whereas the 25OHD Total and 24,25-dihydroxyvitamin D 3 levels were associated with total body BMC (both p < 0.05). No such association was found in overweight or obese children. Conclusions In healthy children, total, bioavailable, and free 25OHD levels comparably reflected lifestyle factors. In normal-weight children, the con-25OHD BioA and con-25OHD Free , but not m-25OHD Free levels, reflected bone mass, as did the 25OHD Total level.