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


VOL.: 21 (1979) (p. 279)

5. Summary of Data Reported and Evaluation

(N.B. - This section should be read in conjunction with the General Remarks on Sex Hormones and with the General Conclusions on Sex Hormones.)

5.1 Experimental data

Oestradiol-17b and its esters were tested in mice, rats, hamsters, guinea-pigs and monkeys by subcutaneous injection or implantation and in mice by oral administration. Its subcutaneous administration resulted in increased incidences of mammary, pituitary, uterine, cervical, vaginal and lymphoid tumours and interstitial-cell tumours of the testis in mice. In rats, there was an increased incidence of mammary and/or pituitary tumours. In hamsters, a high incidence of malignant kidney tumours occurred in intact and castrated males and in ovariectomized females, but not in intact females. In guinea-pigs, diffuse fibromyomatous uterine and abdominal lesions were observed. Oral administration of oestradiol-17b in mice led to an increased mammary tumour incidence. Subcutaneous injections in neonatal mice resulted in precancerous and cancerous cervical and vaginal lesions in later life and an increased incidence of mammary tumours.

Oestradiol-17b has teratogenic actions on the genital tract and possibly on other organs and impairs fertility.

5.2 Human data

No case reports or epidemiological studies on oestradiol-17b alone were available to the Working Group Epidemiological studies on steroid hormones used in oestrogen-progestin oral contraceptive preparations have been summarized in the section, 'Oestrogens and Progestins in Relation to Human Cancer'.

5.3 Evaluation

There is sufficient evidence for the carcinogenicity of oestradiol-17b in experimental animals. In the absence of adequate data in humans, it is reasonable, for practical purposes, to regard oestradiol-17b as if it presented a carcinogenic risk to humans. Studies in humans strongly suggest that the administration of oestrogens is causally related to an increased incidence of endometrial carcinoma; there is no evidence that oestradiol-17b is different from other oestrogens in this respect.

For definition of the italicized terms, see Preamble Evaluation.

Previous evaluation: Vol. 6 (1974)

Subsequent evaluation: Suppl. 7 (1987) (Steroidal oestrogens)

Last updated: 23 April 1998

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