Does place of birth influence endogenous hormone levels in Asian-American women?

Abstract

In 1983-87, we conducted a population-based case-control study of breast cancer in Asian women living in California and Hawaii, in which migration history (a composite of the subject's place of birth, usual residence in Asia (urban/rural), length of time living in the West, and grandparents' place of birth) was associated with a six-fold risk gradient that paralleled the historical differences in incidence rates between the US and Asian countries. This provided the opportunity to determine whether endogenous hormones vary with migration history in Asian-American women. Plasma obtained from 316 premenopausal and 177 naturally premenopausal study controls was measured for levels of estrone (E1), estradiol (E2), estrone sulphate (E1S), androstenedione (A), testosterone (T), dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulphate (DHEAS), progesterone (PROG) and sex hormone-binding globulin (SHBG). Levels of the oestrogens and sex hormone-binding globulin did not differ significantly between Asian- and Western-born women, although among premenopausal women, those least westernised had the lowest levels of E1, E2, and E1S. Androgen levels, particularly DHEA, were lower in women born in the West. Among premenopausal women, age-adjusted geometric mean levels of DHEA were 16.5 and 13.8 nmol l(-1) in Asian- and Western-born women respectively; in postmenopausal women these values were 11.8 and 9.2 nmol l(-1), (P<0.001) respectively. Among postmenopausal women, androgens tended to be highest among the least westernised women and declined as the degree of westernisation increased. Our findings suggest that aspects of hormone metabolism play a role in population differences in breast cancer incidence.

Copyright 2002 Cancer Research UK

Figures

Figure 1

Breast cancer odds ratios for Asian-American women according to migration history. Migration categories are from left to right as follows: born in the East, rural in East, living in West

Figure 2

Oestrogen and SHBG levels in Asian-American women according to migration history. (A) and (B) correspond to levels in pre- and postmenopausal women respectively. Migration categories are from left to right as follows (number of pre- and post-menopausal women in parentheses): born in the East, rural in East, living in West <8 years (10, 5); born in the East, urban in East, living in the West <8 years (37, 9); born in the East, rural in East, living in West 8+ years (26, 11); born in the East, urban in East, living in the West 8+ years (55, 22); born in the West, all grandparents born in the East (137, 56); born in the West, at least one grandparent born in the West (24,2). Excluded are 27 pre-, 12 postmenopausal women missing information on type of residence in the East, number of years living in the West or place of birth of grandparents. Plasma levels of E1, E2 E1S are in pmol l−1; SHBG is in nmol l−1; free E2 is expressed as a per cent.

Figure 3

Androgen levels in Asian-American women according to migration history. (A) and (B) correspond to levels in pre- and postmenopausal women respectively. Migration categories are from left to right as follows (number of pre- and post-menopausal women in paren.): born in the East, rural in the East, living in the West <8 years (10, 5); born in the East, urban in the East, living in the West <8 years (37, 9); born in the East, rural in the East, living in the West 8+ years (26, 11); born in the East, urban in the East, living in the West 8+ years (55, 22); born in the West, all grandparents born in the East (137, 56); born in the West, at least one grandparent born in the West (24,2). Excluded are 27 pre-, 12 postmenopausal women missing information on type of residence in the East, number of years living in the West or place of birth of grandparents. Plasma levels of DHEA, A and T are in nmol l−1; for DHEAS, the level is μmol l−1.