The relationship between vitamin D and adolescents' parathyroid hormone and bone mineral density.

Introduction: To detect the relationship between 25-hydroxy vitamin D (25(OH)D) and adolescents' parathyroid hormone (PTH) and bone mineral density (BMD).

Material and methods: Two hundred adolescent girls were recruited for this cross-sectional comparative study. After detailed evaluation, a pelvic sonography was performed for the studied adolescents to rule out any pelvic pathology. Adolescents' blood samples were collected to measure the thyroid stimulating hormone, prolactin, glycosylated haemoglobin (HbA_1C), PTH, and 25(OH)D. The studied adolescents' BMD and the T-score were evaluated at 2 anatomical sites. The studied adolescents were classified according to their serum 25(OH)D into 2 groups: a 25(OH)D-deficient group (study group; 25(OH)D < 20 ng/ml) and normal controls (25(OH)D > 30 ng/ml). Student's t-test was used for analysis of the studied adolescents' variables, and correlation analysis (Pearson`s correlation) was used to detect the relationship between 25(OH)D and adolescents' PTH and BMD.

Results: The parathyroid hormone was statistically higher in the 25(OH)D-deficient group than in the normal controls (41.3 ±3.4 pg/ml vs. 21.1 ±2.8) (p = 0.02), and the BMD was statistically lower in the 25(OH)D-deficient group than in the normal controls (-1.25 ±0.5 vs. 0.3 ±0.4) (p = 0.01). The 25(OH)D had a significant negative correlation with the adolescents' PTH (r = -0.9175; p < 0.00001) and a significant positive correlation with the adolescents' BMD (r = 0.756; p < 0.00001). The parathyroid hormone had a significant negative correlation with the adolescents' BMD (r = -0.7006; p < 0.00001).

Conclusions: The parathyroid hormone in this study had significant negative correlations with both 25(OH)D and BMD. The 25(OH)D had a significant positive correlation with the studied adolescents' BMD.