Serum Levels of 25-Hydroxyvitamin D and Bone Turnover Markers in Female Basketball Players: Age-Related Differences

The aims of this study were to 1) quantify 25-hydroxyvitamin D [25(OH)D] status during the midpoint of the in-season phase when the sun exposure is lowest (in late Fall); 2) provide age-specific reference data for serum markers of bone turnover in middle adolescent (15–18 years) and late adolescent to early adulthood (19–30 years) female basketball players. Fasting morning blood samples (5 mL) were drawn from an antecubital vein to determine circulating levels of 25(OH)D, osteocalcin, and carboxy-terminal telopeptides of crosslinks of type I collagen (CTx-I). Independent T-test [25(OH)D and osteocalcin] or Mann-Whitney U test (CTx-I) were used to identify differences between groups. Considering 25(OH)D concentration, 21 participants (80.7%) displayed vitamin D insufficiency (50–75 nmol/L), three participants (11.5%) displayed vitamin D deficiency (<50 nmol/L), and two participants (7.7%) were vitamin D sufficient (>75 nmol/L). Significant differences were observed in bone turnover markers (osteocalcin: p = 0.003 and CTx-I: p = 0.03) between groups, whereby middle adolescent female basketball players displayed significantly higher serum levels of osteocalcin (46.1 ± 15.8 ng/ml) and CTx-I (1018.8 ± 271.4 pg/ml) compared to late adolescent to early adulthood female basketball players (osteocalcin: 30.4 ± 7.6 ng/ml and CTx-I: 776.7 ± 240.8 pg/ml). A high prevalence (92.2%) of vitamin D inadequacy (insufficiency and deficiency) was observed in the players examined in our study. Middle adolescent female basketball players possess a higher bone turnover rate than late adolescent to early adulthood female basketball players.