Estimates were calculated separately for males and females, and the difference investigated using a bootstrap Wald test. Combined (male and female) associations were also investigated following adjustment for sex. The difference between the effect of buy PLX4032 25(OH)D2 and 25(OH)D3 was calculated from the bootstrap replicate distribution, and the P values using a Wald test. Minimally adjusted analyses (model 1), which were based on seasonally

adjusted 25(OH)D3 levels or 25(OH)D2, were adjusted for sex, age at pQCT scan, and adjusted for 25(OH)D2 and seasonally adjusted 25(OH)D3, respectively. In model 2, we additionally adjusted for loge-transformed fat mass, lean mass and height. In the final model (model 3), we also adjusted for physical activity and social economic factors (maternal or paternal social class, maternal education). Analyses with endosteal circumference were adjusted for periosteal circumference throughout (endosteal adjusted for periosteal circumference). Sensitivity analyses were

BGJ398 in vivo performed based on model 2 by: (a) adjusting for parathyroid hormone (PTH); (b) restricting those with available puberty information and then, in this subgroup, examining the impact of adjusting for pubertal status (tanner stages IV/V versus earlier stages); and (c) restricting those with 25(OH)D assays collected at age 9.9 years. All analyses were conducted using STATA 11.2(College Station, TX, USA), and data is assumed to be missing at random. Results Descriptive analyses There were 1,709 boys and 1,870 girls with pQCT scans (age 15.5 years), and plasma 25(OH)D2 and 25(OH)D3 (age 7.6, 9.9 or 11.8 years; see Fig. 1). Those who were included in the analysis were of higher maternal and paternal social class compared to those who were not. Boys were taller, heavier and had greater lean mass compared to girls, whereas fat mass was higher in girls (Table 1). BMCC, Glutamate dehydrogenase cortical

bone area, periosteal circumference, endosteal circumference and cortical thickness were greater in boys compared to girls, whereas BMDC was higher in girls. 25(OH)D3 levels were slightly higher in boys and 25(OH)D2 levels slightly higher in girls. PTH levels were slightly higher in girls. There was evidence of weak inverse associations between 25(OH)D2 and height LM and FM, which appeared somewhat stronger in girls compared to boys, e.g. P = 0.06 for gender interaction test for association with height (Table 2). There was little association between 25(OH)D3 and height, and LM P > 0.75, and weak evidence of an association with FM P = 0.06. 25(OH)D3 was inversely related to PTH, whereas no association was seen for 25(OH)D2. There was a very weak association between seasonally adjusted 25(OH)D3 and 25(OH)D2, r = −0.0298 P = 0.155, excluding those subjects in whom 25(OH)D2 was below the assay detection limit. Fig.