INS and obesity due to melanocortin 4 receptor deficiency: AN has been reported in association with IR and other disorders, such as obesity, DM, MS, PCOS, some autoimmune diseases, malignancies (most frequently, gastrointestinal neoplasms and neuroendocrine neoplasia), endocrine tumors, such as acromegaly and Cushing’s syndrome, iatrogenic circumstances or so called drug-induced AN (for instance, local AN due to insulin injections, topic corticotherapy, etc.), and atypical presentations on the nasal crease due to local factors (as seen in patients with persistent itching caused by chronic allergic rhinitis).