Riboflavin and riboflavin-derived cofactors in adolescent girls with anorexia nervosa

Background: Thyroid hormones, riboflavin, riboflavin cofactors, and organic acids were assessed in girls with anorexia nervosa. Objective: The objective was to examine the effect of malnutrition and low thyroid hormone concentrations on erythrocyte and plasma riboflavin metabol ism and their relation with urinary organic acid excretion. Design: Seventeen adolescent girls with anorexia nervosa [body mass index ( BMI; in kg/m(2)): 14.8 +/- 2.2] and 17 age-matched, healthy girls (control subjects; BMI: 20.5 +/- 2.2) took part in the feeding study. Erythrocyte an d plasma riboflavin as well as riboflavin cofactors (flavin mononucleotide and flavin adenine dinucleotide) were assessed by HPLC, whereas urinary org anic acids were assessed by gas chromatography-mass spectrometry. Results: Anorectic patients who began a feeding program had higher erythroc yte riboflavin (3.5 +/- 2.2 compared with < 0.1 nmol/mol hemoglobin: P < 0. 001), lower plasma flavin adenine dinucleotide (57.8 +/- 18.5 compared with 78.5 +/- 54.3 nmol/L; P < 0.05), and higher urinary ethymalonic acid (7.12 +/- 4.39 compared with 1.3 +/- 2.8 mu mol/mmol creatinine; P < 0.001) and isovalerylglycine (7.65 +/- 4.78 compared with 3.8 +/- 0.9 mu mol/mmol crea tinine; P < 0.05) concentrations than did control subjects. Triiodothyronin e concentrations were low and negatively correlated with plasma riboflavin concentrations (r = -0.69, P < 0.01). Not all patients showed improvements in these biochemical indexes after 30 d of refeeding. Conclusions: The low triiodothyronine concentrations observed in anorexia n ervosa could alter the extent of riboflavin conversion into cofactors, thus leading to high erythrocyte riboflavin concentrations, low plasma flavin a denine dinucleotide concentrations, and high rates of ethylmalonic acid and isovalerylglycine excretion.