With the help of babies and more than 5,000 of their diapers, Emory University researchers have developed an accurate, noninvasive method to determine estrogen levels in infants.
The method, previously used in nonhuman primates, will allow researchers to learn more about the association between estrogen levels in human infants and their long-term reproductive development as well as the development of sex-specific behaviors, such as toy preference or cognitive differences. What's more, the method will also allow researchers to look at how early disruption of the endocrine system affects long-term maturation, a growing concern among researchers and physicians.
Surprisingly little is known about hormone levels during human infancy. Previous human research has focused on the measurement of hormones in blood, urine and saliva. The new data are the result of using fecal samples collected from cotton diapers. With this novel approach, the researchers successfully measured the fecal levels of estradiol, a type of estrogen.
The well-known importance of estradiol's role in postnatal development of the body, brain and behavior has in recent years raised specific concerns about how exogenous estrogens, or environmental estrogens, such as those found in soy, fruits and vegetables, plastics and common household items, affect lifelong health.
"The development of robust, noninvasive methods to measure these hormones in infants allows us to further investigate the association between postnatal hormone production and the development of sex-specific biology and behavior," says Michelle Lampl, PhD, MD, Emory University Samuel Candler Dobbs professor of anthropology, and senior author of a paper in Frontiers in Systems Biology describing the new method. The study, conducted by researchers at Emory, the University of North Carolina at Chapel Hill and the University of Virginia Health System, Charlottesville, appears online and in the current issue of Frontiers in Systems Biology.
"The development of an assay to measure estrogen from diapers might initially strike one as unnecessary or strange, but the need is real," says Sara Berga, MD, James Robert McCord professor and chairman, Department of Gynecology and Obstetrics, Emory University School of Medicine.
"We understand very little about the hormonal dynamics that occur during early development precisely because we lack a reliable way to track hormones in neonates and very young children. Having a way to track this critical hormone that influences behavior and the development of many important tissues, including the brain, will allow us to understand normal. This really is a great leap forward, and the investigators should be congratulated on this advance."
The paper's lead author is Amanda L. Thompson, PhD, who conducted the research at Emory and is now assistant professor of anthropology at the University of North Carolina, Chapel Hill. Other authors are corresponding author Michael L. Johnson, PhD, University of Virginia Health System, and Patricia L. Whitten, Emory University.
Because of the ethical and practical difficulties of repeatedly taking blood samples from healthy infants, little data are currently available for charting the developmental pathways of estradiol. As such, existing data describe only the range of variability in hormonal levels--not developmental trends or what that variability might mean when it comes to individual physical and behavioral development.
The study included 32 infants, 15 male and 17 female, aged 7 days to 15 months. The infants' parents retained soiled diapers after each diaper change during a 24-hour period. Bagged diapers were collected and then frozen and stored at -- 80°C and analyzed 24 hours to 12 months after collection. In preparation for analysis, diapers were thawed overnight at 2 to 8°C.
Previous studies in primates have shown a close parallel between fecal levels of estradiol and serum values. Likewise, a comparison of fecal steroid levels between the study infants and previous studies of human adults shows an overlapping pattern, a pattern that is also seen in infant serum when compared with adult serum.
"These observations are the first report of human infant fecal estradiol levels and they provide a new tool for investigating early human development," says Lampl. "Because infant diapers are plentiful, fecal samples can be collected frequently and over a long period of time. Future longitudinal studies will allow the association between fecal levels of steroids and physiological measures to be assessed, and expand our understanding independent of serum measures."
At Emory, Lampl also serves as associate director of the Emory/Georgia Tech Predictive Health Institute.
Lampl's research centers on human growth spurts, with a focus on fetal and infant stages of life. Her current work investigates the relationship between nutrition, immunological and hormonal networks that interact with behavior to influence developmental processes.
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