Browsing by Autor "Vitzthum, Virginia J"

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A prospective study of early pregnancy loss in humans
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 2006) Vitzthum, Virginia J
Objective: To test two hypotheses: In spontaneous conceptions, early pregnancy loss (EPL) is associated with [1] inadequate luteal (ovarian) P, and/or [2] elevated follicular (adrenal) P. Design: A population-based prospective study. Setting: Thirty rural Bolivian communities. Patient(s): Women volunteers (n = 191), 19–40 years old, in stable sexual unions and not using contraception. Intervention(s): Collection of serial saliva samples throughout sequential ovarian cycles and urine samples during late luteal phases. Collections continued throughout pregnancy for each detected conception. Main Outcome Measure(s): Occurrence of spontaneous conceptions and subsequent outcomes. Salivary concen trations of P. Test for elevated urinary human chorionic gonadotropin (hCG). Result(s): Luteal (through implantation) P levels were similar in pregnancies lost within 5 weeks after conception (EPL; n = 8) and those pregnancies that were maintained longer (sustained conceptions, SC; n = 32). Follicular P was significantly higher in EPL than in SC. Conclusion(s): [1] Elevated follicular P was associated with EPL in natural conceptions in healthy women. [2] Early pregnancy loss exhibits absolute luteal P levels comparable to SC, but lower luteal/follicular P ratios. (Fertil Steril 2006;86:373–9. ©2006 by American Society for Reproductive Medicine.)
Assessing salivary progesterone in coca-leaf chewing populations
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 1990) Vitzthum, Virginia J
ABSTRACT. Although there is evidence for reduced fertility in Andean and Himalayan populations at higher altitudes, factors other than hypoxia may be primarily responsible. A potentially valuable approach in the investigation of these fertiüty determinants is the use of salivary steroid assays. However, coca-leaf ehewinga ubiquitous practice amonghigh altitude Andean populations-has negative consequences for the acsurate measurement of ovarian steroids. Ttris report evaluates the effests of coca-leaf chewing on assays of ealivary progesterone. Study participante include naive and habitual users of coca-leaf fmm La Paz and El Alto, Bolivia. Approximately 300 saliva samples were collected immeüately before, dnring, and after coca-leaf chewing. Ttre series includes samples with and without the alkaloid enhancer typically used by coca-leaf chewers. On the basis of this study, an appropriate protocol is developed for the collection of salivary samples in coca-leaf chewing populations. Ttrese reeults highliglrt the necessity of establishing suitable collection procedures before full field implementaüon of saliva sampling.
Does Hypoxia impair ovarian function in Bolivian women indigenous to high altitude?
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 2000) Vitzthum, Virginia J
Abstract. Fertility appears to be reduced in at least some high altitude populations relative to their counterparts at lower elevations. Inferring from the difficulties with reproduction of newcomers to high altitude and from animal experiments, it has been hypothesized that this apparent reduction is the result of hypoxia acting to reduce fecundity and/or increase fetal loss. In humans, however, several behavioral as well as biological factors may affect fertility levels. These many factors have been organized by demographers into a framework of seven proximate determinants that includes fecundability (the monthly probability of conception) of which successful ovulation is one component. To test whether ovarian function is impaired in women indigenous to high altitude, we measured salivary progesterone (P) in a sample (n = 20) of Quechua women (aged 19-42 years) residing at 3100 m. It was found that mean luteal P = 179 pmol/L and mean midluteal P = 243 pmol/L, levels that fall about midway in the range of known values for several populations and are higher than some lower altitude populations. These findings suggest that hypoxia does not appear to significantly impair ovarian function in those with lifelong residence at high altitude. There are, however, several factors common to many high altitude populations that may act to reduce fecundability and fertility including intercourse patterns (affected by marriage and migration practices), prolonged lactation, dietary insufficiency, and hard labor.
Epidemiological transitions, reproductive health, and the Flexible Response Model
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 2003) Vitzthum, Virginia J
Abstract. In concert with improving standards of living since the mid-19th century, chronic and non-infectious diseases replaced infectious diseases as the major causes of mortality in more developed countries. Thus, economic development has been seen as one strategy to improve women's reproductive health. However, rates of ewo of the major contributors to women's illness, maternal mortality and breast cancer, do not correspond well with the level of economic development. Drawing upon our longitudinal study of reproductive functioning among rural Bolivians (Project Reproduction and Ecology in Provincia Aroma (REPA), we propose an evolutionary model to explain variation in certain aspects of women's reproductive health. Our findings suggest new avenues of inquiry into the determinants of reproductive health and have implications for improving the well-being of women worldwide.
Interpopulational differences in progesterone levels during conception and implantation in humans
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 2004) Vitzthum, Virginia J
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.
Salivary progesterone levels and rate of ovulation are significantly lower in poorer than in better-of urban-dwelling Bolivian women
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 2002) Vitzthum, Virginia J
Agriculturalists in less-developed countries (LDC) have lower progesterone levels than urban industrialized populations. However, it is unknown if urban LDC populations are also relatively lower. We tested whether urban Bolivia samples--poorer (Bol-p) and better-off (Bol-b)-- have lower progesterone than a Chicago (USA) sample, and whether progesterone and rate of ovulation are lower in Bol-p than in Bol-b METHODS: Serial salivary samples collected from Bolivians, screened according to strict exclusion criteria during two complete menstrual cycles, were radioimmunoassayed for progesterone; anthropometrics were collected at mid-follicular and mid-luteal phases. RESULTS: Progesterone levels are lower in the Bolivia samples, and higher in the Bol-b than Bol-p; ovulation rate isgreater in Bol-p. For only cycles, mean-follicular-P (pmol/l), mean-luteal-P (pmol/l), and mean-peak-P (pmol/l) are respectively 65, 142 and 208 in Bol-p; 76, 167 and 232 in Bol-b; and 96, 240 and 330 in Chicago. Principal components representing body-size and progesterone level are positively correlated (r = 0.404, P = 0.005). CONCLUSIONS: Progesterone levels appear to be influenced by chronic and acute ecological conditions, evidenced by the association with body-size and the probability of ovulation respectively. These findings have implications for understanding cancer aetiology, developing population-appropriate hormonal contraceptives, and modelling the evolution and functioning of the reproductive system
Salivary/Serum progesterone ratio differs between menstrual cycle phases but not between populations : implications for health, reproductive, and behavioral research
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 2025) Vitzthum, Virginia J
ABSTRACT Objectives: Many investigations of human health, behaviors, and adaptations require an indicator of ovarian cycle functioningas a causal, outcome, or confounding variable in the study design and analyses. Because the dynamic fluctuations in cycle hor-mones can rarely be adequately characterized by a single measurement, but repeated blood sampling can be onerous, salivaryfree progesterone (P Free- SAL) concentration is widely used in both clinical and research contexts as an alternative to total pro-gesterone concentration in venous blood samples (P Total-VEN ). However, some doubts have been raised about the use of P Free- SALbecause of suggestions that Bolivian and other populations and/or individuals might differ markedly in the ratio of P Free- SAL toP Total-VEN (the apparent uptake fraction, UF). If there are such differences, several decades of comparative population researchbased on P Free- SAL would require reconsideration, and a seemingly useful tool in both clinical and research contexts would belost or require additional extensive pre-use evaluations. Such impacts would fall disproportionally on clinical monitoring andresearch studies of menstruating persons, a segment of the population that has long been underrepresented in research and clin-ical trials, especially in low resource conditions. Therefore, we tested three hypotheses: (H1) UF differs by ovarian cycle phase;(H2) UF differs in Bolivian women from that of non-Bolivian women; and (H3) within a population, UF is consistently higher orlower in some individuals than in most others.Methods: We collected mid-follicular and mid-luteal near-concurrent samples of venous blood and saliva from 36 healthy pre-menopausal Bolivian women. P Total-VEN and P Free- SAL were measured using commercial enzyme immunoassays. To test the studyhypotheses, we used graphical and statistical methods to analyze these new data and to analyze data from several previouslypublished studies.Results: In our study sample of Bolivian women, P Free- SAL and P Total-VEN concentrations (n = 66 pairs) were significantly and highlycorrelated (Spearman's rho = 0.858; mixed model: intercept = 77.4 pmol/L [(p < 0.001), β = 0.0191 (p < 0.001)]). An individual's
Seasonal and circadian variation in salivary testosterone in rural Bolivian men
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 2009) Vitzthum, Virginia J
Abstract. Testosterone (T) plays a key role in the increase and maintenance of muscle mass and bone density in adult men. Life history theory predicts that environmental stress may prompt a reallocation of such investments to those functions critical to survival. We tested this hypothesis in two studies of rural Bolivian adult men by comparing free T levels and circadian rhythms during late winter, which is especially severe, to those in less arduous seasons. For each pair of salivary TAM/TPM samples (collected in a 12-h period), circadian rhythm was considered classic (CCLASSIC) if TAM > 110%TPM, reverse (CREVERSE) if TPM > 110%TAM, and flat (CFLAT) otherwise. We tested the hypotheses that mean TAM > mean TPM and that mean TLW < mean TOTHER (LW 5 late winter, OTHER 5 other seasons). In Study A, of 115 TPM–TAM pairs, 51% 5 CCLASSIC, 39% 5 CREVERSE, 10% 5 CFLAT; in Study B, of 184 TAM–TPM pairs, 55% 5 CCLASSIC, 33% 5 CREVERSE, 12% 5 CFLAT. Based on fitting linear mixed models, in both studies TOTHER-AM > TOTHER-PM (A: P 5 0.035, B: P 5 0.0005) and TOTHER-AM > TLW-AM (A: P 5 0.054, B: P 5 0.007); TPM did not vary seasonally, and T diurnality was not significant during late winter. T diurnality varied substantially between days within an individual, between individuals and between seasons, but neither T levels nor diurnality varied with age. These patterns may reflect the seasonally varying but unscheduled, life-long, strenuous physical labor that typifies many non-industrialized economies. These results also suggest that single morning samples may substantially underestimate peak circulating T for an individual and, most importantly, that exogenous signals may moderate diurnality and the trajectory of agerelated change in the male gonadal axis.
Seasonal modulation of reproductive effort during early pregnancy in humans
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 2009) Vitzthum, Virginia J
Abstract. Life history theory predicts that early pregnancy presents a relatively low cost, uncontested opportunity for a woman to terminate investment in a current reproductive opportunity if a conceptus is of poor quality and/or maternal status or environmental conditions are not propitious for a successful birth. We tested this hypothesis in rural Bolivian women experiencing substantial seasonal variation in workload and food resources. Significant risk factors for early pregnancy loss (EPL) included agropastoralism versus other economic strategies, conception during the most arduous seasons versus other seasons, and increasing maternal age. Anovulation rate (AR) was higher during the most arduous seasons and in older women. Breastfeeding and indicators of social status and living conditions did not significantly influence either risk of EPL or AR. Averaged over the year, anovulation occurred in about 1/4 of the cycles and EPL occurred in about 1/3 of the conceptions. This is the first evidence of seasonality of EPL in a non-industrialized population, and the first to demonstrate a relationship between economic activities and EPL. These findings suggest that both anovulation and EPL are potential mechanisms for modulating reproductive effort; such ‘‘failures’’ may also be nonadaptive consequences of conditions hostile to a successful pregnancy. In either case, variation in EPL risk associated with different subsistence activities can be expected to influence fertility levels and birth seasonality in both contemporary and past human populations. These consequences of variability in the risk of EPL can impact efforts to understand the sources of variation in reproductive success.