Abstract
Both vitamin D and insulin-like growth factor 1 (IGF-1) play essential roles in bone metabolism and may interact during prepubertal bone accrual. We investigated the association of low serum 25-hydroxyvitamin D (25(OH)D) (<20 ng/mL) with the circulating bone turnover markers, when compared to their interaction with IGF-1. Subjects and Methods: Serum 25(OH)D, IGF-I, P1NP (N-terminal propeptide of type I procollagen), and CTX-1 (C-terminal telopeptide of type I collagen) were measured, and the bone turnover index (BTI) was calculated in 128 healthy children, aged 9–11 years. Results: Mean 25(OH)D concentration was 21.9 ± 4.9 ng/mL, but in 30.5% of participants it was <20 ng/mL (<50 nmol/L). We observed a trend for higher P1NP (p < 0.05) and IGF-1 (p = 0.08), towards lower 25(OH)D in tertiles. Levels of P1NP in the lowest 25(OH)D tertile (<20 ng/mL) were the highest, while CTX and BTI remained unchanged. Additionally, 25(OH)D negatively correlated with IGF-1, while the correlation with P1NP was not significant. A strong positive correlation of IGF-1 with P1NP and BTI but weak with CTX was observed. Low 25(OH)D (<20 ng/mL) explained 15% of the IGF-1 variance and 6% of the P1NP variance. Conclusions: Low levels of 25(OH)D do not unfavorably alter bone turnover. It seems that serum 25(OH)D level may not be an adequate predictor of bone turnover in children.
Highlights
Optimal bone growth during childhood and adolescence is critical to reach a maximal strength and size of the skeleton
An earlier prospective study in prepubertal girls with sufficient vitamin D status (35.3 ± 9.8 ng/mL) showed that 25(OH)D and insulin-like growth factor 1 (IGF-1) exert a significant impact on bone mineral content (BMC) accrual, assessed by DXA [2]
Another fact worth mentioning is that the association of 25(OH)D with bone accrual was shown to be negative and weaker than positive association of IGF-1 with bone mineral content accrual (BMC) [2]
Summary
Optimal bone growth during childhood and adolescence is critical to reach a maximal strength and size of the skeleton. It is assumed that up to 90% of adult bone mineral content is achieved in early adulthood [1]. The higher the peak bone mass and bone mineral density, the slower the age-related bone loss, and the lower the risk of development of osteoporosis and subsequent fractures. The association of vitamin D status with bone health throughout childhood is subject to change, depending on age and pubertal stage. Studies have suggested a possible interaction between 25-hydroxyvitamin D and IGF-1 during prepubertal bone mineral accrual [2,3]. The key “bone trophic hormones”, growth hormones (GH)
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