Both compounds can modify oestrogenic effects. Progestogen-only contraceptives have growth potentiating effects in the human mammary gland, as indicated by elevated rates of cell proliferation. No data were available on the genetic activity of these progestogens in humans, but norethisterone induced some changes in DNA and chromosomes in experimental systems. Progesterone induced cell transformation in mammalian cells in-vitro . Early studies on use of depot medroxyprogesterone acetate during pregnancy suggested that genital malformations were induced in the fetus, but the results of later studies provided no support for that suggestion.
Medroxyprogesterone acetate administered to men can reduce testosterone levels and semen production.
There is inadequate evidence in humans for the carcinogenicity of progestogen-only contraceptives. There is sufficient evidence in experimental animals for the carcinogenicity of medroxyprogesterone acetate. For definition of the italicized terms, see Preamble Evaluation .