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Author: Rebecca Christine Knickmeyer Publisher: Frontiers Media SA ISBN: 2889196070 Category : Diseases of the endocrine glands. Clinical endocrinology Languages : en Pages : 82
Book Description
There is extensive evidence from animal models that gonadal steroids, produced in fetal and neonatal life, act on the developing organism to produce sex differences far beyond the reproductive system. That early gonadal steroid exposure also plays an important role in human development is supported by studies of individuals with disorders of sex determination and differentiation. It is much less clear whether normal variation in gonadal steroid exposure predicts sexually dimorphic health outcomes or within-sex variation. This is largely due to challenges related to the assessment of gonadal steroid exposure in the developing fetus and neonate. Regarding the prenatal period, serial measurements of serum hormone levels in the fetus, for use in studies of later development, are not possible for ethical reasons. Researchers have measured hormones in maternal blood, umbilical cord blood, and amniotic fluid; used putative anthropometric indices such as the relative lengths of the 2nd and 4th digits (2D:4D); evaluated common variants in genes related to hormone production, transport, and metabolism; and examined development in opposite sex twins and the offspring of mothers with hyperandrogeny. Each of these approaches has particular strengths and notable weaknesses. Regarding the neonatal period, serial measurements in serum are often impractical for studies of typical development. Salivary hormone assays, frequently used in studies of older children and adults, have not been extensively investigated in neonates. The most appropriate timing for testing is also open to debate. Early work suggested that testosterone levels in males begin to rise after the first postnatal week, peak around the 3rd to 4th months of life, and then drop back to very low levels by 1 year. However a more recent study of 138 infants did not demonstrate this pattern. Testosterone was highest on the day of birth and gradually dropped over the first 6 months. Even less is known about patterns of early estrogen exposure, though highly sensitive bioassays indicated that sex differences are present in early childhood. In addition, the design and interpretation of studies may be impacted by widespread acceptance of conceptual frameworks that are not well-supported empirically. For example, many researchers presume that the free hormone hypothesis, which states that unbound hormone is more readily diffusible into tissues and thus a better measure of actual exposure, is true. However this hypothesis has been challenged on multiple grounds. A second example: it is generally accepted that masculinization of the human brain is primarily mediated by the androgen receptor (in contrast to rodents where the estrogen receptor plays a major role), in part because chromosomal males with complete androgen insensitivity generally espouse a female gender identity. However this is not always the case, and other sexually dimorphic outcomes have not been carefully assessed in CAIS. The aim of this research topic is to gather together experimental and review papers which address the diverse challenges in assessing prenatal and neonatal gonadal steroid exposure for studies of human development with the expectation that this will allow more critical appraisal of existing studies, identify critical research gaps, and improve the design of future studies.
Author: Rebecca Christine Knickmeyer Publisher: Frontiers Media SA ISBN: 2889196070 Category : Diseases of the endocrine glands. Clinical endocrinology Languages : en Pages : 82
Book Description
There is extensive evidence from animal models that gonadal steroids, produced in fetal and neonatal life, act on the developing organism to produce sex differences far beyond the reproductive system. That early gonadal steroid exposure also plays an important role in human development is supported by studies of individuals with disorders of sex determination and differentiation. It is much less clear whether normal variation in gonadal steroid exposure predicts sexually dimorphic health outcomes or within-sex variation. This is largely due to challenges related to the assessment of gonadal steroid exposure in the developing fetus and neonate. Regarding the prenatal period, serial measurements of serum hormone levels in the fetus, for use in studies of later development, are not possible for ethical reasons. Researchers have measured hormones in maternal blood, umbilical cord blood, and amniotic fluid; used putative anthropometric indices such as the relative lengths of the 2nd and 4th digits (2D:4D); evaluated common variants in genes related to hormone production, transport, and metabolism; and examined development in opposite sex twins and the offspring of mothers with hyperandrogeny. Each of these approaches has particular strengths and notable weaknesses. Regarding the neonatal period, serial measurements in serum are often impractical for studies of typical development. Salivary hormone assays, frequently used in studies of older children and adults, have not been extensively investigated in neonates. The most appropriate timing for testing is also open to debate. Early work suggested that testosterone levels in males begin to rise after the first postnatal week, peak around the 3rd to 4th months of life, and then drop back to very low levels by 1 year. However a more recent study of 138 infants did not demonstrate this pattern. Testosterone was highest on the day of birth and gradually dropped over the first 6 months. Even less is known about patterns of early estrogen exposure, though highly sensitive bioassays indicated that sex differences are present in early childhood. In addition, the design and interpretation of studies may be impacted by widespread acceptance of conceptual frameworks that are not well-supported empirically. For example, many researchers presume that the free hormone hypothesis, which states that unbound hormone is more readily diffusible into tissues and thus a better measure of actual exposure, is true. However this hypothesis has been challenged on multiple grounds. A second example: it is generally accepted that masculinization of the human brain is primarily mediated by the androgen receptor (in contrast to rodents where the estrogen receptor plays a major role), in part because chromosomal males with complete androgen insensitivity generally espouse a female gender identity. However this is not always the case, and other sexually dimorphic outcomes have not been carefully assessed in CAIS. The aim of this research topic is to gather together experimental and review papers which address the diverse challenges in assessing prenatal and neonatal gonadal steroid exposure for studies of human development with the expectation that this will allow more critical appraisal of existing studies, identify critical research gaps, and improve the design of future studies.
Author: National Academies of Sciences, Engineering, and Medicine Publisher: National Academies Press ISBN: 0309458625 Category : Science Languages : en Pages : 423
Book Description
To safeguard public health, the US Environmental Protection Agency (EPA) must keep abreast of new scientific information and emerging technologies so that it can apply them to regulatory decision-making. For decades the agency has dealt with questions about what animal-testing data to use to make predictions about human health hazards, how to perform dose-response extrapolations, how to identify and protect susceptible subpopulations, and how to address uncertainties. As alternatives to traditional toxicity testing have emerged, the agency has been faced with additional questions about how to incorporate data from such tests into its chemical assessments and whether such tests can replace some traditional testing methods. Endocrine active chemicals (EACs) have raised concerns that traditional toxicity-testing protocols might be inadequate to identify all potential hazards to human health because they have the ability to modulate normal hormone function, and small alterations in hormone concentrations, particularly during sensitive life stages, can have lasting and significant effects. To address concerns about potential human health effects from EACs at low doses, this report develops a strategy to evaluate the evidence for such low-dose effects.
Author: Simon Baron-Cohen Publisher: MIT Press ISBN: 0262524562 Category : Medical Languages : en Pages : 145
Book Description
This pioneering study looks at the effects of prenatal testosterone on postnatal development and behavior. Hormonal effects on behavior have long been studied in animals; the unique contribution of this book is to suggest a connection between human fetal hormones and later behavior. It details for the first time testosterone's effect on social and language development, opening a new avenue of research for cognitive neuroscience. The authors look at samples of amniotic fluid taken during amniocentesis at 16 weeks' gestation, and relate the fetal level of testosterone (which is present in fetuses of both sexes, although in different quantities) to behavior at ages 1, 2, and 4 years. They argue that the amniotic fluid provides a window into the child's past—a chemical record of that child's time in the womb—that allows informed prediction about the child's future brain, mind, and behavior. This is not the retrospective speculation of psychoanalysis, they point out, but an opportunity to study development prospectively and trace developmental precursors and causes of later cognition. The study suggests that prenatal levels of testosterone affect a range of later behaviors in children, from the inclination to make eye contact with others to the size of the vocabulary. It also suggests that prenatal testosterone level may be related to the development of typically "masculine" and "feminine" behaviors. The study's ongoing research explores whether fetal testosterone has any link with the risk of developing autism. Connecting endocrinology and psychology, the authors propose that there is a biological component to behaviors often thought to be produced by the social environment.
Author: Arnold A. Gerall Publisher: Springer Science & Business Media ISBN: 1489924531 Category : Medical Languages : en Pages : 374
Book Description
Based on a large variety of experiments on both humans and animals, this volume presents novel conceptualizations of the organizing consequences of hormones throughout the lifespans of mammals.
Author: National Research Council Publisher: National Academies Press ISBN: 0309048753 Category : Science Languages : en Pages : 402
Book Description
Many of the pesticides applied to food crops in this country are present in foods and may pose risks to human health. Current regulations are intended to protect the health of the general population by controlling pesticide use. This book explores whether the present regulatory approaches adequately protect infants and children, who may differ from adults in susceptibility and in dietary exposures to pesticide residues. The committee focuses on four major areas: Susceptibility: Are children more susceptible or less susceptible than adults to the effects of dietary exposure to pesticides? Exposure: What foods do infants and children eat, and which pesticides and how much of them are present in those foods? Is the current information on consumption and residues adequate to estimate exposure? Toxicity: Are toxicity tests in laboratory animals adequate to predict toxicity in human infants and children? Do the extent and type of toxicity of some chemicals vary by species and by age? Assessing risk: How is dietary exposure to pesticide residues associated with response? How can laboratory data on lifetime exposures of animals be used to derive meaningful estimates of risk to children? Does risk accumulate more rapidly during the early years of life? This book will be of interest to policymakers, administrators of research in the public and private sectors, toxicologists, pediatricians and other health professionals, and the pesticide industry.
Author: Institute of Medicine Publisher: National Academies Press ISBN: 0309132975 Category : Medical Languages : en Pages : 287
Book Description
It's obvious why only men develop prostate cancer and why only women get ovarian cancer. But it is not obvious why women are more likely to recover language ability after a stroke than men or why women are more apt to develop autoimmune diseases such as lupus. Sex differences in health throughout the lifespan have been documented. Exploring the Biological Contributions to Human Health begins to snap the pieces of the puzzle into place so that this knowledge can be used to improve health for both sexes. From behavior and cognition to metabolism and response to chemicals and infectious organisms, this book explores the health impact of sex (being male or female, according to reproductive organs and chromosomes) and gender (one's sense of self as male or female in society). Exploring the Biological Contributions to Human Health discusses basic biochemical differences in the cells of males and females and health variability between the sexes from conception throughout life. The book identifies key research needs and opportunities and addresses barriers to research. Exploring the Biological Contributions to Human Health will be important to health policy makers, basic, applied, and clinical researchers, educators, providers, and journalists-while being very accessible to interested lay readers.
Author: Rebecca Christine Knickmeyer
Author: Rebecca Christine Knickmeyer
Author: 
Author: National Academies of Sciences, Engineering, and Medicine
Author: 
Author: Simon Baron-Cohen
Author: Arnold A. Gerall
Author: 
Author: National Research Council
Author: National Institutes of Health (U.S.). Division of Research Grants
Author: Institute of Medicine