Research papersestrogenlinks to cancer

oestrogen and breast cancer

One study did not specify the hormonal status of participants [ 68 ], and one study was conducted on perpartum women [ 69 ] and two studies on postpartum women [ 7071 ].

Voluntary changes in most of the important reproductive risk factors such as parity and ages at menarche and menopause are not realistic, but extended breast feeding will produce a small decrease in breast cancer risk, in addition to its benefits for the child. This article explores the evidence for the hypothesis that exposure to oestrogen is a major determinant of risk for breast cancer.

It may be that, in postmenopausal women at least, testosterone is converted to oestrogen in the breast.

how do hormones affect cancer

Several studies have found women with the low-activity COMT allele to be at higher risk for breast cancer [ 45 - 47 ]. In premenopausal women, the predominant form of circulating oestrogen is oestradiol secreted by the ovaries in cyclical monthly patterns.

Since this criterion does not discriminate between studies, it was not considered in the assessment of the overall risk of bias for each study.

Is estradiol linked to breast cancer

Whenever required, a second review author CD was consulted. Results from numerous animal studies suggest that high intake of soy may confer a protective effect against breast cancer [ 67 ], but the findings from studies in humans remain equivocal [ 68 ]. Introduction The practice of regular physical activity is recommended worldwide by different public health agencies [ 1 ] for primary or secondary prevention of many health problems, including cancers [ 2 , 3 ]. Such polymorphisms might be particularly important among postmenopausal women, in whom oestrogen production is not homeostatically controlled by pituitary gonadotrophins. Oral contraceptives and breast cancer In , data from 54 published studies on use of the combined contraceptive pill containing an oestrogen and a progestogen in relationship to breast cancer risk were brought together in a pooled analysis [ 53 ]. Because breast cancer itself might affect hormone production, it is necessary to conduct prospective studies of oestrogens and breast cancer risk in which samples are collected at the start of the study from healthy women, who are then followed up with respect to cancer diagnoses. Similarly, the prescription of hormone replacement therapy HRT for older women, containing oestrogens with or without progestins, has become common.

The importance of ovarian steroidogenesis in normal breast development and in the genesis of breast cancer is highlighted by the facts that early menarche and late menopause are associated with greater breast cancer risk, whereas late menarche and early menopause, that occurring before 40 years of age, result in a significant reduction of the same 17 - The researchers found that compared with women who never used MHT, women who did had a significantly higher risk of developing invasive breast cancer.

The data were extracted first as reported by the studies, and then transformed as required [ 16 ].

Do hormones cause cancer

Three major mechanisms are postulated to be involved in their carcinogenic effects: stimulation of cellular proliferation through their receptor-mediated hormonal activity, direct genotoxic effects by increasing mutation rates through a cytochrome Pmediated metabolic activation, and induction of aneuploidy. Epidemiological studies have also firmly established associations between risk for breast cancer and other reproductive factors, including nulliparity having no children or low parity, late age at first birth, and breast feeding [ 10 ]. This combination of measures at the end of follow-up and measures of change is based on the assumption of comparability of baseline measures for the two groups provided by randomization. As these chemopreventatives may themselves be associated with detrimental effects, clinicians try to identify women at particularly high risk for breast cancer, for whom benefits of such interventions are likely to outweigh the risks [ , ]. No restriction was applied regarding who administered the intervention physical activity professionals, health professionals, or researchers. Polymorphisms in genes such as COMT, which is involved in the methylation of oestrogens to harmless metabolites, have been the subject of epidemiological studies [ 44 ]. These results are compatible with the oestrogen hypothesis, but the numbers studied are too small, and the difficulties of appropriate adjustment for day of menstrual cycle too complex, to allow any firm conclusions. This intriguing field relates to the suggestion that certain perinatal factors are associated with high concentrations of maternal oestrogens in pregnancy [ 78 ] or high levels of oestrogens in the infant postnatally [ 85 ]. A pre-established protocol was drawn up, in which the primary outcome was the difference in circulating estradiol concentrations between the physical activity experimental and the control groups after intervention. These findings support the possibility that exposure to phyto-oestrogens at critical periods of development might be an important determinant of risk for breast cancer. When the values at the end of follow-up were not reported, the value of the observed change after the intervention MDs before—after intervention for each group was used [ 16 ].

Other lifestyle changes that may have protective effects mediated by oestrogens include minimising alcohol consumption and taking regular physical exercise. Progestins, like oestrogens, are thought to exert their effects mainly through binding to nuclear receptor proteins.

how does oestrogen cause breast cancer
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Oestrogen exposure and breast cancer risk