The Relationship Between Calciotropic Hormones, IGF-1, and Bone Mass Across Pubertal Stages.

BACKGROUND: Little is known about the changes in calciotropic hormones during puberty and their relationship to bone mass during this critical period for skeletal accretion.

OBJECTIVES: Investigate changes in calciotropic hormones, IGF-1, body composition, and their associations with bone metabolism in adolescents.

METHODS: Post hoc analyses were performed from data on 335 healthy school children, ages 10-17 years, with hypovitaminosis D who participated in a vitamin D randomized controlled trial. Baseline serum biochemistries; hormonal studies; densitometry at the spine, hip, and total body; and body composition were used. ANOVA and regression analyses were implemented to evaluate changes in variables of interest across pubertal stages, within and between genders.

RESULTS: Bone mass and body composition parameters increased substantially across Tanner stages in both genders. Serum calcium, 1,25-dihydroxyvitamin D, and 25-hydroxyvitamin D levels did not vary by Tanner stages in both genders. Conversely, serum phosphorus, alkaline phosphatase, IGF-1, PTH, and osteocalcin peaked for the most part at Tanner stage II in girls and stage III in boys. 1,25-Dihydroxyvitamin D correlations with bone mass were not consistent, whereas IGF-1 was the most robust correlate of bone mass at several skeletal sites in early Tanner stages in both genders (R = 0.3-0.6).

CONCLUSION: Serum phosphorus, alkaline phosphatase, IGF-1, PTH, and osteocalcin, but not calcium or 1,25-dihydroxyvitamin D, increased significantly in early puberty, with gender difference except for PTH, peaking earlier in girls than in boys. IGF-1 is a robust predictor of bone mass, an effect mediated in large part by increments in lean mass.