Testicular regression syndrome (TRS) is a developmental anomaly characterized by the absence of one or both testicles with partial or complete absence of testicular tissue. TRS may vary from normal male with unilateral no-palpable testis through phenotypic male with micropenis, to phenotypic female. The phenotype depends on the extent and timing of the intrauterine accident in relation to sexual development. The disease is Testicular regression syndrome (Orphanet_983). Also known as: ETRS, Embryonic testicular regression syndrome, TRS, Vanishing testes syndrome, Vanishing testis syndrome.