SERUM LEPTIN CONCENTRATIONS IN PATIENTS WITH ANOREXIA-NERVOSA, BULIMIA-NERVOSA AND NONSPECIFIC EATING DISORDERS CORRELATE WITH THE BODY-MASS INDEX BUT ARE INDEPENDENT OF THE RESPECTIVE DISEASE

OBJECTIVE Leptin, the product of the ob gene, is a recently discovered hormone secreted by adipocytes. Serum leptin concentrations increase in correlation with the percentage of body fat, but little else is kno wn about the physiological actions of leptin in humans. The aim of thi s study was to determine the role of leptin in severe eating disorders , and whether its levels are correlated with the specific disease or e xclusively with body weight. TESTS Serum concentrations of human lepti n were analysed by specific radioimmunoassay and compared with the ind ividual body mass indexes (BMI). The correlations between serum leptin concentrations and BMI, age and height were analysed. PATIENTS A tota l of 65 women were studied: 25 patients with anorexia nervosa, 20 wome n with bulimia nervosa, 6 women with a diagnosis of nonspecific eating disorder, and 14 normal-weight women who acted as controls. At the ti me of the study, the patients were non-cured, under treatment, and at different stages of therapeutic evolution. MEASUREMENTS Plasma leptin levels were measured by specific radioimmunoassay. RESULTS The mean se rum leptin in the normal-weight women was 10.5 +/- 1.1 mu g/l, compare d with 7.6 +/- 1.1 mu g/l in the anorexia nervosa patients (P<0.05). T his reduction in leptin levels was paralleled by the differences in BM I (21.4+/-0.4 vs 18.8 +/- 0.2) P<0.05. These differences between the c ontrols and anorexia nervosa patients were not observed in patients wi th bulimia nervosa who had a mean serum leptin level of 9.9 +/- 1.4 mu g/l and BMI of 21.3 +/- 0.6, neither significantly different from con trols. On the contrary, patients with non-specific eating disorders sh owed a large reduction in BMI (17.9 +/- 1.2, P<0.05 vs control), and a parallel reduction in serum leptin levels, 4.5 +/- 1.0 (P<0.05 vs con trols). When individual values of leptin were plotted against BMI a wi de range was observed in all groups; in the control subjects from 5.6 to 17.7 mu g/l, in anorexia nervosa patients from 2.1 to 28.1 mu g/l, in patients with bulimia nervosa between 2.6 and 25.9 mu g/l, and in w omen with non-specific eating disorder from 2.0 to 8.9. No correlation was observed with the specific disease but in each group a significan t correlation was observed only with BMI. CONCLUSIONS Serum leptin lev els in three groups of patients affected by severe eating disorders ar e not related to the specific pathology but are correlated with the in dividual BMI. The analysis of leptin values may be a useful index of a ssessing the adipose tissue stores in the clinical setting, but will b e of no help for diagnosis nor prognosis of severe eating disorders.