Physical work causes suppression of ovarian function in women

Jasieńska, Grażyna; Ellison, Peter T.

doi:10.1098/rspb.1998.0511

Cited by 138 publications

(89 citation statements)

References 25 publications

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“…The presence of mothers-in-law was still beneficial even when variables for anthropometric status were included in the model (results not shown). This suggests that the higher fertility was not solely due to higher nutritional status of women with living mothers-in-law (though this analysis does not control for workload, which has been shown to have independent effects on fecundity: Jasienska & Ellison, 1998). In this patrilocal community, women tend to live with their mothers-in-law rather than their mothers so mothers-in-law may be able to share domestic work with their daughters-in-law.…”

Section: Discussionmentioning

confidence: 98%

The effects of kin on female fertility in rural Gambia

Sear

Mace

McGregor

2003

Evolution and Human Behavior

118

126

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This is an electronic version of an Article published in Evolution and AbstractHuman females reproduce relatively rapidly throughout their reproductive years compared to the other great apes. It has been suggested that women are able to sustain this rapid pace by co-opting family members to help raise their children. We tested the hypothesis that the presence of kin will increase the reproductive rates of women using a longitudinal database collected from rural Gambia. We found that both the husband's mother and, to a lesser extent, the husband's father increased the probability that a woman would give birth. A woman's parents, however, had no effect on her fertility rate, nor did her elder sisters or co-wives. The presence of a woman's elder brothers even decreased her probability of giving birth. There was no evidence that elder children acted as 'helpers at the nest', as the existence of living elder children slowed down rather than increased birth rates. We suggest that the increased fertility in the presence of mothers-in-law may be due to these women helping out their daughters-in-law with domestic and subsistence duties. Given that it is paternal, rather than maternal, relatives who increase fertility, social pressures on women from older kin to bear many children may also be important.

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Section: Discussionmentioning

confidence: 98%

The effects of kin on female fertility in rural Gambia

Sear

Mace

McGregor

2003

Evolution and Human Behavior

118

126

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“…For example, average progesterone was lower in Nepalese, Polish, and Congolese women during seasons of food shortage and͞or increased work demands compared to relatively less stressful seasons in the respective populations (11)(12)(13), and progesterone was lowered by moderate weight loss in a study of U.S. women (28).…”

Section: Figmentioning

confidence: 99%

“…In U.S. women, relatively lower progesterone is associated with subfecundity among patients at infertility clinics, perhaps signaling failure to ovulate or luteal insufficiency (7), and is also associated with a reduction in risk of conception (8). Yet studies of women from nonindustrialized populations have consistently observed progesterone levels averaging only about two-thirds of the average levels of U.S. women (9)(10)(11)(12)(13). Does the typically much lower progesterone observed among women in nonindustrialized populations signal a significant impairment of reproductive function relative to U.S. women?…”

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confidence: 99%

“…This population was chosen because of widespread chronic undernutrition, often accompanied by physically demanding labor, and a nearly universal lack of contraceptive use at the time of the study. Two prior cross-sectional studies of Bolivian high-altitude natives (9, 10) had observed progesterone levels comparable to other nonindustrialized populations (11)(12)(13), arguing against an effect of altitude on progesterone in these women. Also like these populations, progesterone was significantly lower than in samples of U.S. women (14,15).…”

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confidence: 99%

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Interpopulational differences in progesterone levels during conception and implantation in humans

Vitzthum

Spielvogel

Thornburg

2004

Proc. Natl. Acad. Sci. U.S.A.

102

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Clinical studies of women from the United States demonstrate a sensitivity of the ovarian system to energetic stress. Even moderate exercise or caloric restriction can lead to lower progesterone levels and failure to ovulate. Yet women in many nonindustrial populations experience as many as a dozen pregnancies in a lifetime despite poor nutritional resources, heavy workloads, and typical progesterone levels only about two-thirds of those of U.S. women. Previous cross-sectional studies of progesterone may, however, suffer from inadvertent selection bias. In a noncontracepting population, the most fecund women, who might be expected to have the highest progesterone, are more likely to be pregnant or breastfeeding and hence unavailable for a crosssectional study of the ovarian cycle. The present longitudinal study was designed to ascertain whether lower progesterone also characterizes conception, implantation, and gestation in women from nonindustrialized populations. We compared rural Bolivian Aymara women (n ‫؍‬ 191) to women from Chicago (n ‫؍‬ 29) and found that mean-peak-luteal progesterone in the ovulatory cycles of Bolivian women averaged Ϸ71% that of the women from Chicago. In conception cycles, progesterone levels in Bolivian women during the periovulatory period were Ϸ63%, and during the peri-implantation period were Ϸ50%, those of the U.S. women. These observations argue that lower progesterone levels typically characterize the reproductive process in Bolivian women and perhaps others from nonindustrialized populations. We discuss the possible proximate and evolutionary explanations for this variation and note the implications for developing suitable hormonal contraceptives and elucidating the etiology of cancers of the breast and reproductive tract.I n an evaluation of demographic data from populations worldwide, Bongaarts (1) concluded that, except in cases of famine, nutritional factors play a relatively minor role in determining human fecundity (capacity to conceive) or fertility (number of live births). Despite characteristically marginal nutritional status and the demands of arduous activities, women in less developed countries often average seven to eight pregnancies, some having 12 or more during a lifetime. Differences among populations, or reductions from a theoretical maximum, appear fully attributable to a limited set of behavioral and physiological proximate fertility determinants apparently little affected by nutritional factors. If neither fecundity nor fertility is thus significantly influenced, neither is fecundability (the monthly probability of conception). Yet clinical studies of women from the United States indicate a sensitivity of ovarian function to both relatively low energy intake and͞or high energy expenditure. The most extreme response, failure to ovulate, may occur in the face of only moderate energetic stress (2-4) and, of course, reduces fecundity and fecundability to 0. Short of anovulation, milder disruptions of ovarian function may also reduce fecundability. Why should o...

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“…Many sources of this variation have been identified. Levels of ovarian hormones are sensitive to factors related to fetal development (11,12), childhood growth (13), and adult life (14)(15)(16)(17)(18)(19)(20)(21)(22). It is also likely that variation in sex-steroid levels results partly from genetic variation (i.e., polymorphism of genes that control steroid hormone biosynthesis; refs.…”

Section: Introductionmentioning

confidence: 99%

CYP17Genotypes Differ in Salivary 17-β Estradiol Levels: A Study Based on Hormonal Profiles from Entire Menstrual Cycles

Jasieńska¹,

Kapiszewska

Ellison

et al. 2006

Cancer Epidemiology, Biomarkers &Amp; Prevention

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Variation in the levels of sex-steroid hormones results from differences in developmental conditions, adult lifestyle, and genetic polymorphism. Genes involved in sex-steroid biosynthesis have been implicated to influence levels of hormones in premenopausal women, but the results were inconclusive. We tested variation among women in levels of salivary estradiol (E 2 ) corresponding to CYP17 genotypes. CYP17 encodes cytochrome P450c17A, which mediates two enzymes important in E 2 synthesis. In contrast to the earlier studies that relied on one or a few samples for assessing the E 2 levels of an individual woman, our study is based on daily collected saliva samples for one entire menstrual cycle. Sixty Polish women, ages 24 to 36 years, with regular menstrual cycles and no reported fertility problems participated in the study. Women with A2/A2 genotype had 54% higher mean E 2 levels than women with A1/A1 genotype (P = 0.0001) and 37% higher than women with A1/A2 genotype (P = 0.0008). Heterozygous A1/A2 women had 13 % higher E 2 levels than homozygous A1/A1 women (but this difference was significant only in a nonparametric test). Levels of E 2 during the day with highest E 2 (day À1) were 72% higher in A2/A2 compared with A1/A1 (P = 0.01) and 52 % higher compared with A1/A2 (P = 0.03). Our results suggest that CYP17 genotype may serve as a biomarker of endocrine function in women of reproductive age. (Cancer Epidemiol Biomarkers Prev 2006;15(11):2131 -5)

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Physical work causes suppression of ovarian function in women

Cited by 138 publications

References 25 publications

The effects of kin on female fertility in rural Gambia

The effects of kin on female fertility in rural Gambia

Interpopulational differences in progesterone levels during conception and implantation in humans

CYP17Genotypes Differ in Salivary 17-β Estradiol Levels: A Study Based on Hormonal Profiles from Entire Menstrual Cycles

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