On the other hand, hypothalamo–pituitary–adrenocortical (HPA)-axis dysregulation is confirmed to be an important parameter for treatment outcome in MD by Schüle and coworkers [19], although dysfunction of the HPA system as determined by the classical dexamethasone (DEX)/corticotrophin releasing hormone (CRH) test as well as with other neuroendocrine assays, seems to be neither a necessary nor a sufficient determinant for acute treatment response. The gene discussed is CRH; the disease is Menkes disease.