Growth hormone (GH) and insulin-like growth factor-I (IGF-I) are known as the somatotropic axis. This chapter discusses research concerning changes in the somatotropic axis due to anorexia nervosa (AN) as well as the possible effects of this axis on further symptoms in patients with AN. In AN, temporary GH resistance has been observed. After recovery of body weight, a normal growth hormone pattern returns. Due to GH resistance, IGF-I levels are low in AN patients and depend on body mass index. This might be because sufficient food intake is required for an adequate liver response to GH with normal IGF-I production. In addition, leptin is suspected to link food intake and caloric restriction with IGF-I. To date, it remains unclear whether IGF-I affects crucial neural processes and psychic symptoms in patients with AN. However, it certainly affects concomitant symptoms, such as osteoporosis, in patients with AN.