“…The first step is to clarify the genetic etiology of individual disorders. In this Special Issue, we elucidate the genetic etiology in combined pituitary hormone deficiency in consanguineous Sudanese families [ 4 ], in idiopathic short stature [ 5 ], in Klinefelter syndrome [ 6 ], and in NNT-related primary adrenal insufficiency [ 7 ], which greatly facilitates the search for etiological elucidation of these rare disorders. However, genetic background has a major impact on endocrine manifestations not only in monogenic disorders but also in complex diseases, as illustrated in morbid obesity [ 8 ].…”