31 R. Strumia (ed.), Eating Disorders and the Skin, DOI 10.1007/978-3-642-29136-4_4, © Springer-Verlag Berlin Heidelberg 2013 4 Endocrine abnormalities are common in patients suffering from eating disorders. They represent an adaptive phenomenon that could determine several complications. These abnormalities tend often to ameliorate with improvement of eating behavior and/or normalization of body weight. The main endocrine changes involve the hypothalamic-pituitary-gonadal axis (HPG), the hypothalamic-pituitary-adrenal axis (HPA), the hypothalamic-pituitary-thyroid axis, the hypothalamic-growth hormone-somatomedin axis, and some central and peripheric neuro- peptides too. The central nervous system, responding to external and endogenous stimuli, transmits its messages via neurotransmitters/neuromodulators. These are sent also to the hypothalamus, which exerts its influence on the pituitary. In the hypo- thalamus, connections between central nervous and endocrine system occur; in fact, hypothalamic neurons receive signals both from the central ner- vous structures and from the endocrine glands. 4.1 Hypothalamic-Pituitary- Gonadal Axis (HPG) Amenorrhea, defined as the absence of at least three consecutive periods, is a current diagnostic criterion for AN that will not be present in the next classification of eating disorders (DSM-5) [1]. In AN, plasma concentrations of LH, FSH, and estrogens are lower than normal, featuring a so- called hypogonadotropic hypogonadism. The cir- cadian secretion of LH and FSH resembles that in the prepubertal stage, with blunted spontaneous secretory pulses during both the day and the night. Moreover, the gonadotropin response to exogenous GnRH is low or absent as in prepuber- tal stage; these patients show a normal negative feedback of estrogens on the HPG axis but no positive feedback, this latter capacity being acquired in the late phases of the pubertal matu- ration. This phenomenon may result from inhibi- tion of the transformation (aromatization) of androgens into estrogens, which normally occurs in the adipose tissue, poorly represented in AN [2]. However, it has been demonstrated that in some patients amenorrhea precedes body weight loss and persists after the recovery of a normal weight, so that the former hypothesis of the “critical body weight” to explain these endocrine abnor- malities takes no more place. Factors other than body weight changes have to be searched to explain the HPG axis dysfunctions of anorexic patients: increased physical activity, increased tonus of endogenous opioids, and neuropeptide dysregulations. Endocrine Abnormalities in Eating Disorders Giovanni Scanelli, Paolo Schlagenauf, and Linda Degli Esposti G. Scanelli, M.D. () • P. Schlagenauf, RD • L.D. Esposti Medical Department, Eating Disorders Unit, University Hospital of Ferrara Arcispedale Sant’Anna, Corso della Giovecca, 203, I-44121 Ferrara, Italy e-mail: g.scanelli@ospfe.it