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.