The impact of developmental conditions on adult salivary estradiol levels: Why this differs from progesterone?

Abstract

Women living in energetically stressful conditions have significantly lower baseline salivary steroid levels compared to those in affluent environments. Developmental hypotheses suggest that interpopulation variation in ovarian function results from contrasting environments experienced during growth. We use a migrant study of Bangladeshi women to test this hypothesis. We compared middle-class women (19-39 years) who migrated to London, UK, at different life-stages (pre and postmenarche), with Bangladeshi sedentees, second-generation British-Bangladeshis, and white British women living in similar London neighborhoods (total n = 227). We analyzed levels of salivary estradiol for one menstrual cycle, together with data on anthropometry, diet, lifestyle, and migration and reproductive histories. Results from multiple linear regression models, controlling for anthropometric and reproductive variables, show no significant differences in baseline estradiol levels between groups whether all cycles or just ovulatory cycles are analyzed. We also found no correlation between age at migration or time since migration on estradiol levels, nor between adult estradiol levels and age at menarche. Our results differ from previous reports of significantly lower salivary estradiol levels in populations living in more extreme ecological settings. They also contrast with our previous findings of significant intergroup differences in baseline levels of salivary progesterone. However, women who spent their childhood in Sylhet have a lower proportion of ovulatory cycles compared to women who developed in Britain. These group differences in ovulation frequency indicate more qualitative effects of contrasting developmental environments. We discuss possible explanations for differences in response between progesterone and estradiol, as well as broader implications of our findings.

Ethnicity or environment: effects of migration on ovarian reserve among Bangladeshi women in the United Kingdom

“…In an earlier paper, we found that infectious disease load was a significant predictor of age at menopause among a larger sample of Bangladeshi women, but this variable was not significant in the analyses here of a smaller group of women sampled for hormone levels (60). We have similarly suggested, however, in past papers that life history trade-offs could explain differences in other reproductive and developmental parameters between Bangladeshis who grow up in contrasting UK and Bangladeshi environments, including ages at adrenarche and menarche, levels of salivary progesterone and rates of ovulation (41)(42)(43)84).…”

“…In our earlier work, for example, we found significant differences in levels of reproductive steroids, length of the reproductive lifespan, and rates of ovulation among age-and socioeconomically matched Bangladeshi women depending on whether they had grown up in Bangladesh or the UK (32,(41)(42)(43).…”

Total estradiol levels in migrant and British‐born British Pakistani women: Investigating early life influences on ovarian function

“…Four women who migrated before the age of 8 were excluded from the analyses because of suggestions that early life influences on ovarian function may extend up until the age of adrenarche or puberty (Ellison, 1996a; Nú ñ ez-de la Mora et al, 2007Mora et al, , 2008. The remaining sample size was 79 (Table 1).…”

“…Both the fraction of hormone that is free and that bound to albumin are considered bioavailable. Following the recent development of reliable assays of salivary free estradiol, anthropologists have often chosen to use daily assessments to compare levels of free estradiol in saliva samples either collected over the whole cycle or for specific phases of the cycle (Lu et al, 1999; Nú ñ ez-de la Mora et al, 2008). Only free estradiol can be assessed in saliva, as bound estradiol does not cross from blood to saliva.…”

“…Nú ñ ez-de la Mora et al (2007) reported that women who grew up in Bangladesh and then migrated to London had luteal phase salivary progesterone levels that were not significantly different from those of sedentee women in Bangladesh, whereas women of Bangladeshi origin who were born in the UK had salivary progesterone levels that were significantly higher than those of sedentee women in Bangladesh. However, there were no differences in salivary free estradiol levels at any stage of the menstrual cycle between women in Bangladesh and either women of Bangladeshi or European origin living in the UK (Nú ñ ezde la Mora et al, 2008).We set out to test Ellison's hypothesis by comparing estradiol levels in women currently living in the same environment (urban north-east England) but who grew up in different environments (either rural Pakistan or the UK). We tested the specific predictions that British Pakistani women born and raised in Pakistan would have lower levels of total estradiol than British Pakistani women born in the UK, and that British Pakistani women born and raised in the UK would have levels of total estradiol not significantly different from those of women of European origin born and raised in the UK.…”