The presence of an "X" factor or factors as a cause of human sterility.
D005260:Female; D001556:Hexachlorocyclohexane; D006801:Humans; D007246:Infertility; D007247:Infertility, Female / Q000209:etiology*; D008297:Male
D001556:Hexachlorocyclohexane; C034873:hexachlorocyclohexane x-factor
STERILITY, FEMALE/etiology and pathogenesis