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
See Also:
Toxicological Abbreviations
Norethisterone and Norethisterone Acetate (IARC Summary & Evaluation, Volume 21, 1979)