MEN1 and neoplasm: These differences may be caused by the complexity of the biological regulation of miRNA expression and the fact that miRNA changes in the blood may not only derive from intrinsic changes within tumor cells and their release into the circulation, but may also be altered due to the host immune response or inflammatory reactions, as well as by the fact that, in the case of complex diseases, such as MEN1, in which different and multiple tumors may occur in a single patient, levels of specific circulating miRNAs can be the result of these multiple tumors rather than of a single pathology.