Glucocorticoids and Body Fat Inversely Associate With Bone Marrow Density of the Distal Radius in Healthy Youths

CONTEXT Elevated bone marrow adipose tissue (BMAT) is associated with lower bone quality, higher fracture rates, and an unfavorable overall metabolic profile. Apart from age, particularly glucocorticoids (GC), body fat, and diet are discussed to influence BMAT. We hypothesized that already in healthy youths, higher fat intake, higher fat mass index (FMI), and higher GC secretion, still within the normal range, may associate with increased BMAT. DESIGN In a subsample of healthy 6- to 18-year-old participants of the Dortmund Nutritional and Anthropometric Longitudinally Designed Study, peripheral quantitative CT of the nondominant proximal forearm was used to determine bone marrow density of the distal radius as an inverse surrogate parameter for BMAT. In those participants (n = 172) who had collected two, 24-hour urines within around one year before bone measurement, major urinary GC metabolites were measured by gas chromatography-mass spectrometry and summed up to assess daily adrenal GC secretion (ΣC21). Dietary intake was assessed by 3-day weighed dietary records. FMI was anthropometrically calculated. Separate multiple linear regression models were used to analyze the relationships of ΣC21, FMI, and fat intake with BMAT. RESULTS After controlling for confounders, such as age, energy intake, and forearm muscle area, ΣC21 (β = -0.042) and FMI (β = -0.002) showed inverse relationships with bone marrow density (P < 0.05), whereas fat intake did not associate significantly. CONCLUSION Our results indicate that already a moderately elevated GC secretion and higher body fatness during adolescence may adversely impact BMAT, an indicator for long-term bone health.