Anti-müllerian hormone (AMH) is a glycoprotein that is produced by immature Sertoli cells and is responsible for the regression of müllerian ducts in male fetuses. It is a useful marker of testicular function in children, when anorchia is suspected and in intersex states. In the persistent müllerian duct syndrome, both AMH-positive and AMH-negative forms have been reported. In three cases of the latter, a mutation of the AMH gene is thought to have been responsible for the condition.