Plasma concentrations of vitamin D metabolites in pubertal girls with anorexia nervosa

Plasma concentrations of 25-hydroxyvitamin D (25-OHD), 1,25-dihydroxyvitamin D (1,25-(OH)2D), 24,25-dihydroxyvitamin D (24,25-(OH)2D) and vitamin D-binding protein (DBP) were measured in 12 pubertal girls (aged 10-18 yr) with anorexia nervosa in relapse. The results were compared with similar data obtained in 81 healthy girls representing all stages of puberty. The patients with anorexia nervosa had significantly lower 1,25-(OH)2D levels (71 vs. 124 pmol/l; p less than 0.0005), and significantly higher 24,25-(OH)2D levels (6.0 vs. 3.2 nmol/l; p less than 0.0005), whereas the 25-OHD concentrations were similar in the two groups (85.7 vs. 86.7 nmol/l). The molar ratios of 24,25-(OH)2D to 25-OHD, which reflects the relative activity of the 24-hydroxylation, were significantly higher in the anorectics (6.6% vs. 3.6%; p less than 0.0005). The mean level of DBP did not differ between the two groups, and accordingly the calculated "free-fraction of 1,25-(OH)2D" was significantly lower in the anorectic patients (p less than 0.0005). It appears that the regulatory mechanisms of the vitamin D endocrine system are altered in the patients with anorexia nervosa at puberty resulting in a relative decrease of the plasma concentration of 1,25-(OH)2D and increase of the 24,25-(OH)2D concentration.