Interpopulational differences in progesterone levels during conception and implantation in humans
Fecha
2004-02-10Autor
Vitzthum, Virginia J
Spielvogel, Hilde
Thornburg, Jonathan
Metadatos
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Clinical studies of women from the United States demonstrate a
sensitivity of the ovarian system to energetic stress. Even moder
ate 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 noncontra
cepting population, the most fecund women, who might be ex
pected to have the highest progesterone, are more likely to be
pregnant or breastfeeding and hence unavailable for a cross
sectional 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 ~71% that of the women from
Chicago. In conception cycles, progesterone levels in Bolivian
women during the periovulatory period were ~63%, and during
the peri-implantation period were ~50%, 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 varia
tion and note the implications for developing suitable hormonal
contraceptives and elucidating the etiology of cancers of the breast
and reproductive tract.