Serum oestrogen levels in postmenopausal women: comparison of American whites and Japanese in Japan

Abstract

Summary Serum oestrone (El), oestradiol (E2) and sex hormone binding globulin (SHBG) levels were studied in postmenopausal Japanese women in Japan (n = 91) and postmenopausal American white women (n = 38). The Japanese women were deliberately chosen to be from a rural agricultural area in order to get samples which represent as closely as possible the traditional Japanese 'lifestyle' that gave rise to the low rates of breast cancer in Japan. El levels were 47%, and E2 levels 36%, greater in the American women; these differences were only reduced to 43% and 27% after adjustment for the lower weight of the Japanese. These results were all statistically highly significant. There was little difference in SHBG levels between the Japanese and the American women. These results for El and E2 could be an important part of the explanation why Japanese and American breast cancer rates continue to diverge further after the menopause.There is considerable evidence that oestrogens are involved in the aetiology of breast cancer and that increased blood levels of oestrogen in postmenopausal breast cancer patients are one marker of high risk (Key & Pike, 1988;Bernstein et al., 1990). The incidence rates for breast cancer in Japan are substantially lower than those in the USA and European countries (Muir et al., 1987), and some systematic pathological and clinical differences between breast cancer diagnosed in Japan and western countries have been reported (Wynder et al., 1963;Chabon et al., 1974). These observations suggest that there may be important differences in endocrine function among residents in these areas, but there are surprisingly few data on blood hormone levels in healthy populations from these countries. We report here a study comparing serum oestrogen and sex-hormone-binding globulin (SHBG) levels of post-menopausal Japanese women in Japan to those of white women in the USA. Subjects and methodsThe Japanese subjects were volunteers residing in rural areas of Miyagi, a prefecture in north-east Japan. These women were mainly from rice farming families. We first contacted them at a general medical screening clinic for the healthy elderly sponsored by their farmer's union, informing them of the purpose of our study and asking for their cooperation. The subjects in the USA were American non-Latino volunteers from a retirement community in Southern California, who had a blood sample drawn during a well-patient visit to a local health clinic. All women had to have intact ovaries, be postmenopausal, and be 60 to 70 years of age. Ninety-one women were sampled in Japan; 38 women were sampled in California. Women with any past or present endocrine disease, or who had used steroid hormones during the previous 12 months, or had more than 12 months total use of steroid hormones, were excluded.All subjects were asked to provide information on a series of factors related to breast cancer risk and, possibly, to hormonal status, including ages at menarche, menopause, and first full-term pregnancy, number of children, and present h...

Effects of a low-fat high-carbohydrate diet on plasma sex hormones in premenopausal women: results from a randomized controlled trial

“…In post-menopausal women it has been found that American whites have oestradiol levels three times those of recent Asian migrants to Hawaii (Goldin et al, 1986). Similar results have been found in a comparison of rural Japanese women and white women living in southern California (Shimizu et al, 1990). These observations are consistent with the hypothesis that oestrogens play an important role in the aetiology of breast cancer.…”

Ethnic differences in post-menopausal plasma oestrogen levels: high oestrone levels in Japanese-American women despite low weight

“…The low oestrogen levels of post-menopausal women living a traditional lifestyle in Japan (Shimizu et al, 1990) were not observed in the Japanese-American women we studied, most of whom (27 of 30) were born in the USA. Geometric mean plasma E1 levels were in fact highest in Japanese-American women, and their geometric mean plasma E2 levels were very close to those of Whites.…”

“…Studies of plasma oestrogen concentrations in 'traditional' Asians (living in Asia) compared with Whites have found lower concentrations in the Asians (Goldin et al, 1986;Key et al, 1990;Shimizu et al, 1990). In particular, a study of post-menopausal Japanese women in Miyagi and non-Latina White women in Southern California found a 32% lower level of plasma oestrone (E1) and a 27% lower level of plasma oestradiol (E2) in the Japanese women (Shimizu et al, 1990).…”

“…Studies of plasma oestrogen concentrations in 'traditional' Asians (living in Asia) compared with Whites have found lower concentrations in the Asians (Goldin et al, 1986;Key et al, 1990;Shimizu et al, 1990). In particular, a study of post-menopausal Japanese women in Miyagi and non-Latina White women in Southern California found a 32% lower level of plasma oestrone (E1) and a 27% lower level of plasma oestradiol (E2) in the Japanese women (Shimizu et al, 1990).Breast cancer incidence rates in Japanese-American women now approach those of non-Latina White women (Ziegler et al, 1993). We therefore investigated whether post-menopausal plasma oestrogen and androstenedione (A; precursor of E1) levels in Japanese-American women were accordingly similar to those in (non-Latina) White women.…”

Active and passive smoking and breast cancer risk in middle‐aged Japanese women

“…10,11 Genetic differences concerning important metabolic enzymes, for example, higher frequency of a variant allele of cytochrome P450 1A1 gene, were reported, 37 and endogenous estrogen levels and the number of estrogen receptors have been reported to differ between Japanese and Caucasians. 38,39 Thus, an association between smoking and breast cancer might appear more readily in Japanese. The incidence of breast cancer among premenopausal women (88/90,161 person-year) was almost the same as that among postmenopausal women (90/107,241 person-year), and the association observed in premenopausal women was strong.…”