The presence of a uterus and fallopian tubes in an otherwise phenotypically normal male is due to

Remember that the Mullerian structures appear during embryonic development in both males and females. Female gonads do not secrete Mullerian-inhibiting factor (MIF), and the Mullerian structures persist. Male testes secrete MIF, which causes regression of Mullerian structures. Anything that prevents MIF secretion in genetic males will result in persistence of Mullerian structures into the postnatal period. Persons who appear to be normal males but who possess a uterus and fallopian tubes have such a failure of Mullerian-inhibiting factor. Their karyotype is 46, XY, testes are present, and testosterone production is normal. When the testes are located intraabdominally, orchidectomy is required to prevent malignant degeneration in these ectopic gonads.