Estradiol

Carcinogenicity

Description of key information

No studies are available for Estradiol and therefore, all data presented are based on the result of a literature search (references are stated in the tables). Estradiol and its esters were tested in mice, rats, hamsters and guinea-pigs by oral and subcutaneous administration. Administration to mice increased the incidences of several tumors including mammary, uterine or renal tumors. In rats, there was an increased incidence of mammary and/or pituitary tumours and an increased incidence of hepatocellular adenomas in males. 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. A report of the IARC Working Group stated that a number of studies, utilizing a variety of designs, have shown a consistent, strongly positive association between exposure to a number of oestrogenic substances and risk of endometrial cancer in human, with evidence of positive dose-response relationships both for strength of medication and duration of use. Users of postmenopausal estrogen therapy had no excess risk for cancers at other sites. The evidence for the carcinogenicity of postmenopausal combined estrogen-progestogen therapy was deemed to be limited.

Justification for classification or non-classification

The following self classification for estradiol is recommended according to Regulation (EC) No.1272/2008 (CLP) :

Carc. 2 (H351)

The classification is in accordance with German legislation for classification of estrogenic steroid hormones. The German Committee on Hazardous Substances (AGS) recommended for estrogenic steroid hormones classification as:

Toxicity to reproduction - Fertility: Category 1A

Toxicity to reproduction - Development: Category 2

Carcinogenicity: Category 2

See Technical Rule for Hazardous Substances 905; elaborated by the German Committee on Hazardous Substances (AGS) and published by the German Federal Ministry of Labour and Social Affairs, version: 19.04.2016, only available in German,URLhttp://www.baua.de/de/Themen-von-A-Z/Gefahrstoffe/TRGS/Begruendungen- 905-906.html.

The associated documentation and justification for grouping steroid hormones and their classification was published in 09/1999. Estradiol is mentioned in attachment 2 on page 16.

Additional information

A registration of estradiol was already submitted earlier and is public available on the ECHA website. Chapter 7, which is still valid from today's perspective, was amended to fulfill the current information requirements. Consequently the migrated data (IUCLID 5 to IUCLID 6) was kept unchanged and only modified if there was a need for further information and/or to pass the technical completeness check (TCC).

 

Animal data

 

 

Test system	Substance	Application	Test concentration	End point/Effect	Literature
C3H/HeJ mice, female	Estradiol	Oral	0.015, 0.15, or 0.75 mg/kg bw/d from week 6 to week 110.   Sacrified after 52 weeks	Preneoplastic and neoplastic findings in mice sacrificed after up to 104 weeks on the estrogenic diets.   High doses of estradiol increased the incidence of adenosis but did not affect the incidence of ovarian tubular adenomas. After 66- 91 weeks of treatment, high doses of estradiol also increased the incidence of mammary gland hyperplastic alveolar nodules	Highman et al., 1980. J. Environ. Pathol. Toxicol., 4, 81-95 as cited by Toxicological Evaluation of certain Veterinary Drug Residues in Food. WHO Food Additives Series: 43, prepared by the Fifty-second meeting of the Joint FAO/WHO Expert Committee on Food Additives (JECFA), 2000.
C3H/HeJ mice	17ß- Estradiol	In drinking- water	0.5 mg/l for 1 y	17ß-Estradiol caused tumours	Welsch,1976. J. Toxicol. Environ. Health, Suppl. 1, 161-175as cited by Toxicological Evaluation of certain Veterinary Drug Residues in Food. WHO Food Additives Series: 43, prepared by the Fifty-second meeting of the Joint FAO/WHO Expert Committee on Food Additives (JECFA), 2000.
B6C3F1 mice, both sexes	Catechol Estrogens	intraperitoneal injection	Treatment on days 12-15 after birth, monitored for 18 months	Estrone-3,4-quinone was significantly carcinogenic in the livers of male mice. It was also highly toxic, as most of the mice died from unknown causes shortly after treatment. Estrone was protective against liver tumour formation in this system, and few tumours were induced in female mice	Cavalieri et al., 1997. Proc. Natl Acad. Sci. USA, 94, 10937-10942 as cited by Toxicological Evaluation of certain Veterinary Drug Residues in Food. WHO Food Additives Series: 43, prepared by the Fifty-second meeting of the Joint FAO/WHO Expert Committee on Food Additives (JECFA), 2000.
Syrian hamsters, male	Estradiol	subcutaneous implantation	25 mg, sacrified after 175 d	Renal tumours in 4/5 animals	Liehr et al., 1986 J. Steroid Biochem., 24, 353-356as cited by Toxicological Evaluation of certain Veterinary Drug Residues in Food. WHO Food Additives Series: 43, prepared by the Fifty-second meeting of the Joint FAO/WHO Expert Committee on Food Additives (JECFA), 2000.
Syrian hamsters, male, castrated	Estradiol	subcutaneous implantation	released 100-210 µg/d for 9 months	Renal tumour incidence: 75-100%,	Li et al., 1983. Cancer Res., 43, 5200-5204356 as cited by Toxicological Evaluation of certain Veterinary Drug Residues in Food. WHO Food Additives Series: 43, prepared by the Fifty-second meeting of the Joint FAO/WHO Expert Committee on Food Additives (JECFA), 2000.
Syrian hamsters, male, castrated	various steroidal and non- steroidal estrogens	Subcutan implantation	Release rate: 110 µg/d for 9 months	Good correlation among the hormonal parameters progesterone receptor induction and serum prolactin and relative estrogenic potency (estrogen receptor   binding) in hamster kidney. All animals trested with estradiol developed renal tumours.	Li et al., 1995. Cancer Res., 55, 4347-4351 as cited by Toxicological Evaluation of certain Veterinary Drug Residues in Food. WHO Food Additives Series: 43, prepared by the Fifty-second meeting of the Joint FAO/WHO Expert Committee on Food Additives (JECFA), 2000.
Syrian hamsters, male, castrated	Estradiol	subcutaneous pellets	Release rate: Estradiol, 96 µg/d for 8 months	tumour incidence of 100%, completely abolished by concurrent treatment with ethinylestradiol	Li et al., 1998 Carcinogenesis, 19, 471-477 as cited by Toxicological Evaluation of certain Veterinary Drug Residues in Food. WHO Food Additives Series: 43, prepared by the Fifty-second meeting of the Joint FAO/WHO Expert Committee on Food Additives (JECFA), 2000.
Syrian hamsters, male,  Orchiectomized	Estradiol	Implants every three months	20 mg	Renal-cell dysplasia and infiltrating and non-infiltrating renal carcinoma were observed.	Goldfarb & Pugh, 1990. Cancer Res., 50, 113¿119 as cited by IARC Monographs, Volume 72, Hormonal Contraception and Post-Menopausal Hormonal Therapy, 1999.
Rat, male and female	Combinations of various estrogens and progestogens	Diet		Increased incidence of hepatocellular   Adenomas in males	Schuppler. & Gunzel, 1979. Arch. Toxicol., Suppl. 2, 181¿195 as cited by IARC Monographs, Volume 72, Hormonal Contraception and Post-Menopausal Hormonal Therapy, 1999.
Sprague- Dawley rats, female	mestranol + norethynodrel	Diet	100 µg + 25 mg for nine months (daily intakes of 0.02¿ 0.03 and 0.5¿0.75 mg/kg bw.)	A statistically significant increase in the number of altered g-glutamyl Transpeptidase- positive hepatic foci was observed	Yager & Yager, 1980. Cancer Res., 40, 3680¿3685 as cited by IARC Monographs, Volume 72, Hormonal Contraception and Post-Menopausal Hormonal Therapy, 1999.
Fischer 344 rats, female	Estradiol dipropionate	Subcutaneous injection	5 mg once every two weeks for 13 weeks	Pituitary adenomas and carcinomas were observed.	Satoh et al., 1997 Toxicol. Pathol., 25, 462¿469 as cited by IARC Monographs, Volume 72, Hormonal Contraception and Post-Menopausal Hormonal Therapy, 1999.
ACI rats	Estradiol	Subcutaneous implantation	27.5 mg (crystalline estradiol)	rapid development of palpable mammary tumours (carcinomas, 100% of the animals), which were first observed 99 days after treatment	Shull et al., 1997. Carcinogenesis, 18, 1595¿1601 as cited by IARC Monographs, Volume 72, Hormonal Contraception and Post-Menopausal Hormonal Therapy, 1999.
Guinea-pigs	Estradiol, Estradiol 3- benzoate	Subcutaneous injection	20-80 µg   3 times a week	Multiple tumors, described as fibromas and fibromyomas	Lipschütz et al., 1938. C.R. Soc. Biol. 130, 9-11 as cited by IARC Monographs, Volume 72, Hormonal Contraception and Post-Menopausal Hormonal Therapy, 1999.
Nonhuman	17ß- Estradiol			In vivo carcinogenicity studies   Positive	Panel Report: EMICBACK/67174 ; Mutat. Res. 185:1-195,1987 as cited by GENETOX database, Beta- Estradiol, last update 1998

 

 

Human data

 

End point/Effect	Literature
Pooled relative risks and 95% confidence intervals derived in a meta-analysis of studies of post-menopausal estrogen therapy and endometrial cancer         Any use of estrogens       Analysis Relative Risk 95% Confidence Interval No. Of Studies All eligible studies 2.3 2.1-2.5 29 Cohort studies 1.7 1.3-2.1 4 Case-control studies 2.4 2.2-2.6 25 Hospital controls 2.2 2.0-2.5 10 Gynaecologcial controls 3.3 2,7-4.0 6 Community controls 2.4 2.0-2.9 10                 Dose of conjugated estrogens (mg)     Analysis Relative Risk 95% Confidence Interval No. Of Studies 0.3 3,9 1.6-9.5 3 0.625 3.4 2.0-5.6 4 >1.25 5.8 4.5-7.5 9                 Duration of use (years)     Analysis Relative Risk 95% Confidence Interval No. Of Studies <1 1.4 1.0-1.8 9  1 - 5 2.8 2.3-3.5 12  5 - 10 5.9 4.7-7.5 10 >10 9.5b 7.4-12 10                 Regimen       Analysis Relative Risk 95% Confidence Interval No. Of Studies Intermittent and cyclic 3 2.4-3.8 8 Continuous 2.9 2.2-3.8 8         Type of estrogen       Analysis Relative Risk 95% Confidence Interval No. Of Studies Conjugated 2.5 2.1-2.9 9 Synthetice 1.3 1.1-1.6 7         Time since last use (years)       Analysis Relative Risk 95% Confidence Interval No. Of Studies <1 4.1 2.9-5.7 3  1 - 4 3.7 2.5-5.5 3 >5 2.3 1.8-3.1 5         Stage of tumour       Analysis Relative Risk 95% Confidence Interval No. Of Studies 0-1 4.2 3.1-5.7 3 39848 1.4 0.8-2.4 3 Not invasive 6.2 4.5-8.4 4 Invasive 3.8 2.9-5.1 6 Death from endometrial cancer 2,7 0.9-8.0 3	Grady et al., 1995. Obstet. Gynecol., 85, 304-313 as cited by Toxicological Evaluation of certain Veterinary Drug Residues in Food. WHO Food Additives Series: 43, prepared by the Fifty-second meeting of the Joint FAO/WHO Expert Committee on Food Additives (JECFA), 2000.
It was determined that there is sufficient evidence in humans for the carcinogenicity of postmenopausal estrogen therapy, largely based on the clear evidence and substantial strength of the association with risk for endometrial cancer. The rise and fall of incidence of endometrial cancer in several areas of the USA was compatible with trends in estrogen use. The association with breast cancer is weak but consistent with biological mechanisms such as the adverse effects of delay in age at menopause and obesity in postmenopausal women. Users of postmenopausal estrogen therapy had no excess risk for cancers at other sites. The evidence for the carcinogenicity of postmenopausal combined estrogen-progestogen therapy was deemed to be limited.	IARC Working Group, 1999 as cited byToxicological Evaluation of certain Veterinary Drug Residues in Food. WHO Food Additives Series: 43, prepared by the Fifty-second meeting of the Joint FAO/WHO Expert Committee on Food Additives (JECFA), 2000.
It was determined that there was sufficient evidence in humans for the carcinogenicity of combined oral contraceptives. Conversely, the evidence for the carcinogenicity of progestogen-only contraceptives was deemed inadequate. It is impossible to infer whether the association between breast cancer and use of combined oral contraceptives is due to earlier diagnosis of breast cancer in users, to the biological effects of contraceptives, or to a combination.	IARC Working Group, 1999 as cited byToxicological Evaluation of certain Veterinary Drug Residues in Food. WHO Food Additives Series: 43, prepared by the Fifty-second meeting of the Joint FAO/WHO Expert Committee on Food Additives (JECFA), 2000.

 

 

 

Determination of the estrogen and estrogen metabolite profiles in prospectively collected serum from post-menopausal women with and without breast cancer who reported no use of exogenous hormones at the time of blood collection. There was a statistically significant association of unconjugated estradiol, unconjugated estrone, conjugated estrone, and many estrogen metabolites with an increased beast cancer risk. Three metabolic pathway ratios were identified that were associated with the risk of breast cancer even after adjustment for circulating levels of unconjugated estradiol: the ratio of the 2-hydroxylation pathway to parent estrogens, the ratio of the 2-hydroxylation pathway to the 16-hydroxylation pathway, and the ratio of 4-hydroxylation pathway catechols to 4-hydroxylation pathway methylated catechols. The ratio of the 2-hydroxylation pathway to parent estrogens was associated with a statistically significantly decreased risk of breast cancer after adjustment for unconjugated estradiol. Compared with estrogens and other estrogen metabolites, 2-hydroxylation pathway catechols have relatively low affinities for estrogen receptors and are rapidly cleared from circulation. Thus, 2-hydroxylation may result in a decrease in bioavailable estrogens and reduced estrogen receptor–mediated signaling in the breast. the ratio of catechols to methylated catechols in the 4-hydroxylation pathway was associated with statistically significantly increased risk of breast cancer. Catechols in both the 2- and 4-hydroxylation pathways can be oxidized to form quinones; these reactive electrophiles can then react with DNA to form a variety of adducts. Methylation of the catechols prevents their conversion to reactive quinones. Whereas the most common DNA adducts derived from 4-hydroxylation pathway catechols are depurinating and highly mutagenic, most of those derived from 2-hydroxylation pathway catechols are stable and can be repaired with little error; this difference may explain why 2-hydroxylation pathway catechols are not potent carcinogens in animal models of estrogen-mediated cancers and why their ratio to the corresponding methylated catechols was not statistically significantly associated with the risk of breast cancer in this study. The results point to three estrogen-related factors that may contribute to breast cancer pathogenesis in postmenopausal women: the quantity of available estrogens, the extent of 2-hydroxylation of parent estrogens, and the extent of methylation of 4-hydroxylation pathway catechols.	Fuhrmann B.J. et al., 2012, J Natl Cancer Inst 2012;104:326–339, Estrogen Metabolism and Risk of Breast Cancer in Postmenopausal Women
Published findings on breast cancer risk associated with different types of menopausal hormone therapy (MHT) are inconsistent, with limited information on long-term effects. The authors bring together the epidemiological evidence, published and unpublished, on these associations, and review the relevant randomised evidence. Every MHT type, except vaginal oestrogens, was associated with excess breast cancer risks, which increased steadily with duration of use and were greater for oestrogen-progestagen than oestrogen-only preparations. The oestrogen-progestagen risks during years 5–14 were greater with daily than with less frequent progestagen use. For a given preparation, the RRs during years 5–14 of current use were much greater for oestrogen-receptor-positive tumours than for oestrogen-receptor-negative tumours, were similar for women starting MHT at ages 40–44, 45–49, 50–54, and 55–59 years, and were attenuated by starting after age 60 years or by adiposity (with little risk from oestrogen-only MHT in women who were obese). After ceasing MHT, some excess risk persisted for more than 10 years; its magnitude depended on the duration of previous use, with little excess following less than 1 year of MHT use. Interpretation: for women of average weight in developed countries, 5 years of MHT, starting at age 50 years, would increase breast cancer incidence at ages 50–69 years by about one in every 50 users of oestrogen plus daily progestagen preparations; one in every 70 users of oestrogen plus intermittent progestagen preparations; and one in every 200 users of oestrogen-only preparations. The corresponding excesses from 10 years of MHT would be about twice as great. Among postmenopausal women in western countries, ER+ breast cancer accounts for about three-quarters of all breast cancer cases and deaths, and post menopausal oestrogenic activity is a strong determinant of the incidence of ER+ breast cancer. Among postmenopausal women, the incidence of ER+ breast cancer correlates with age at menopause 9 and with blood oestrogen levels, and randomised trials have shown that the incidence of ER+ breast cancer can be greatly reduced by anti-oestrogen drugs such as an aromatase inhibitor, or tamoxifen. MHT use is associated with much greater proportional increases in ER+ than ER– disease. Moreover, the excess breast cancer risks in MHT users are strongly duration dependent. Although MHT users differ in various ways from non-users, these biologically plausible findings suggest that the excess of ER+ breast cancer associated with MHT use, which accounts for most of the overall excess of breast cancer associated with MHT use, is largely causal (ie, that some years of MHT use, starting at around the time of the menopause, increases the probability of developing ER+ breast cancer among otherwise similar women of the same age). In Sum, an increase in the risk of developing breast cancer after MHT use was provided, however, this increase is dependent on several factors such as type of MHT, duration of MHT, start of MHT and time after last use. Further, elevation of risk was also dependent on BMI. The lowest risk excess among the MHT users were found in oestrogen-only users, especially in obese women.	Lancet 2019; 394: 1159–68, Type and timing of menopausal hormone therapy and breast cancer risk: individual participant meta-analysis of the worldwide epidemiological evidence