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International Agency for Research on Cancer (IARC) - Summaries & Evaluations

NORETHISTERONE AND NORETHISTERONE ACETATE

VOL.: 6 (1974) (p. 179)

5. Summary of Data Reported and Evaluation

(N.B.: This section should be read in conjunction with the section 'General Conclusions on Hormones'.)

5.1 Animal carcinogenicity data

Norethisterone or its acetate were tested in mice by oral administration and by subcutaneous implantation and in rats by oral administration. When administered alone to mice norethisterone increased the incidence of benign liver-cell tumours in males, of pituitary tumours in females and produced a low incidence of microscopic ovarian tumours in females. The acetate alone only increased the incidence of benign liver-cell tumours in males.

Norethisterone in combination with mestranol, or the acetate in combination with ethinyloestradiol, increased the incidence of pituitary tumours in both sexes. In addition, norethisterone in combination with ethinyloestradiol increased the incidence of pituitary tumours in female mice.

In rats, norethisterone alone increased the incidence of benign liver-cell tumours in males. In combination with mestranol it increased the incidence of benign liver-cell tumours in males and of malignant mammary tumours in both sexes. Norethisterone acetate in combination with ethinyloestradiol increased the incidence of benign mammary tumours in males in one study and increased the incidence of benign liver-cell and mammary tumours in both sexes in a further study.

5.2 Human carcinogenicity data

No case reports or epidemiological studies on norethisterone or its acetate alone were available. Epidemiological studies on steroid hormones used in oestrogen-progestin contraceptive preparations have been summarized in the section, "Oestrogens and Progestins in Relation to Human Cancer", in this volume.

Subsequent evaluations: Vol. 21 (1979); Suppl. 7 (1987) (Progestins; Combined oral contraceptives)


Last updated: 18 March 1998






















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