VOL.: 21 (1979) (p. 461)
When given alone, norethynodrel increased the incidence of pituitary tumours in mice of both sexes and of mammary tumours in castrated males of one strain; it also increased the incidence of liver-cell, pituitary and mammary tumours in male rats.
When given in combination with mestranol, it increased the incidence of pituitary, mammary, vaginal and cervical tumours in female mice, of pituitary tumours in male mice, of mammary tumours in castrated male mice, of benign liver-cell tumours in male rats and of malignant mammary tumours in rats of both sexes. The study in hamsters was of too short duration to be considered for evaluation.
Oral administration of norethynodrel in combination with mestranol to Macaca mulatta monkeys for 5 years did not increase the incidence of mammary tumours; the study is still in progress.
Norethynodrel was reported to be embryolethal in some species and to have teratogenic effects in mice.
For definition of the italicized terms, see Preamble Evaluation.
Previous evaluation: Vol. 6 (1974)
Subsequent evaluation: Suppl. 7 (1987) (Progestins; combined oral contraceptives)
See Also: Toxicological Abbreviations Norethynodrel (IARC Summary & Evaluation, Volume 6, 1974)