Mammary Carcinogenesis in Female and Male Mite Receiving Contraceptives or Gestagens

Three widely used estrogen-progestin mixtures (Enovid, Ovulen, and Lutestral) and their gestagens were investigated as potential carcinogens in the mammary gland of C3H, Rill, and (C3H × RIII)F1 intact female mice. The various contraceptives, despite their estrogen content, did not accelerate or raise the frequency of mammary carcinogenesis in these animals. Norethynodrel and chlormadinone acetate significantly delayed the appearance of the tumors. All three contraceptives produced, with a high rate and after short latencies, mammary cancers in castrated (C3H × RIII)F1 males. Norethynodrel was as potent as mestranol. Chlormadinone acetate did not produce mammary cancers in these males. Some castrated control males developed spontaneous mammary carcinomas late in life, probably induced by adrenal secretions. The castrated male mouse of susceptible strains seems promising material for the establishment of a potential carcinogenic risk for the mammary gland.