Endocrine Abstracts

Introduction: Trials on children and adolescents with excess weight are limited and lack parathyroid hormone (PTH) measures as a surrogate marker of vitaminD status in skeletal health. The present study addresses this key knowledge gap with the use of a dose-response randomized clinical trial (RCT) aimed at determining vitamin D requirement to increase 25(OH)D and suppress PTH concentrations in overweight and obese school children.

Methods: The current study was a single-blind RCT. A total of 378 children and adolescents, 6–13y of age, with age- and sex-specific body mass index (BMI) Z-score≥1 (WHO criteria) were recruited into the study. Participants were allocated to receive 600, 1000, and 2000 IU/d for 12 months. We measured dietary vitamin D, and serum 25(OH)D, PTH, calcium, phosphorus, and alkaline phosphatase at baseline, 6 and 12 months. In this intention-to-treat analysis, the intervention effect in dose level and overall time pattern, we fit a mixed effect model involving a random effect of participants within treatment groups and fixed effects of dose, time, and their interactions.

Results: Participants’ mean(SD) age was 9.3(1.7) y; 52.3% were boys with BMI z scores of 2.55(0.73). The median (IQR) for 25(OH)D were 11.5(8.9), 11.7(10.5), 12.2(10.2) ng/mL at baseline and 23.1(8.0), 25.6(8.3), 28.6(10.4) ng/mL at the end of 12 months in 600, 1000, and 2000IU/d, respectively (P for group<0.0001; P for time<0.0001). Adjusting covariates did not change dose and time main effects (P<0.0001 and 0.021, respectively). Prevalence of vitamin D deficiency (<20 ng/mL) was 80.2, 77.5, and 75.5% in 600, 1000, and 2000 IU vitamin D daily at baseline, respectively, which returned to 34, 18.4, and 7.5% at the end of 12 months. The pattern of PTH response to 600 and 2000IU/d vitamin D was a slight increase at 6 months and a decrease at 12 months. The median (IQR) for PTH were 42.1(38.4), 38.8(29.9), 37.2(39.7) pg/mL at baseline and 44.9(20.5), 45.2(19.6), 43.9(20.8) at 12 months in 600, 1000, and 2000 IU vitamin D daily, respectively (P for group=0.111; P for time<0.0001). After adjusting covariates, time still had a significant main effect (P=0.001).

Conclusion: Children with excess weight benefited from daily supplementation of 1000 and 2000 IU/d compared with 600 IU/d in increasing 25(OH)D, but no evidence on suppression of PTH was found.