Effect of gender, puberty, and vitamin D status on biochemical markers of bone remodedeling

Peak bone mass, a determinant of osteoporosis at older ages, is affected by genetic, nutritional, lifestyle, and hormonal factors. Adolescence is a critical time for peak bone mass accrual, and boys achieve a higher peak bone mass than girls. We have reported vitamin D insufficiency in adolescents in our population, but its impact on bone remodeling is unclear. We systematically evaluated the impact of puberty, gender, and vitamin D status on biochemical markers of bone remodeling. Serum osteocalcin (OC), bone alkaline phosphatase (BAP), C-terminal telopeptide of type I collagen crosslinks (S-CTX), and 25 OH vitamin D were measured in 172 healthy students from private schools in the fall of 1999: There were 92 girls and 80 boys, age 10-17 years. In girls, all markers of bone turnover changed significantly with pubertal stage, were maximal at midpuberty, and decreased toward adult levels by Tanner stage V. Conversely in boys, these markers increased during early pubertal stages but had not normalized by Tanner stage V. Levels of all biochemical markers were significantly higher in boys compared to girls even after adjustment for age, body weight, and Tanner stage, P < 0.0001. In the subgroup of girls, those with vitamin D insufficiency, serum levels of BAP and S-CTX were highest. However, in multiple regression analyses, gender was the only consistent correlate of all three markers of bone remodeling. In conclusion, after adjusting for age, weight, and Tanner stages, changes in bone remodeling markers were most powerfully affected by gender. The latter may have important implications on gender differences in peak bone mass.