Anorexia nervosa (AN) is a severe mental disorder that is characterized by restriction of energy intake, low weight, and endocrine abnormalities. One of the known endocrine changes in relation to underweight is in the GH/IGF-I axis. The aim of the study was (a) to investigate longitudinal characteristics of the IGF-I-change during therapy and weight gain in adult AN, (b) to determine relationships between IGF-I and leptin, (c) to characterize patients with weak and pronounced hormonal reactions to underweight.