PRL and pituitary gland adenoma: MiR-15a and miR-16-1, which belong to the same cluster of tumor suppressor miRNAs, were found to be down-regulated both in GH-secreting and prolactin-secreting pituitary adenomas (49) and were recently confirmed to be down-regulated also in pituitary tumors isolated from mice heterozygote knockout for the Menin 1 (MEN1) gene, which encodes for the tumor suppressor Menin (50).