KCNJ5 and adenoma: Patients with APA carrying KCNJ5 mutations displayed markedly elevated concentrations of the hybrid steroids 18-oxocortisol and 18-hydroxycortisol in the peripheral plasma, which is presumably caused by the underlying histology of these adenomas with a predominant composition of zona fasciculata-like cells and an increased expression of CYP17A1 [40,41].