Doctoral Dissertation Improvement: More than just birth weight: a longitudinal study of the reproductive ecology of infant growth and development

最近的流行病学研究强调了胎儿和婴儿发育对终身生理和健康的重要性。虽然婴儿的生长速度已被理论化，以程序化的方式决定未来的生理功能和成人慢性疾病的风险，密集的纵向调查的婴儿躯体生长是罕见的，躯体生长和激素的发展之间的关系，这种增长的基础还没有得到很好的理解。事实上，婴儿期是一个敏感的时期，在此期间，生长和发展的克里思是根据突出的环境变量而形成的。这种形成是由内分泌系统介导的，但其潜在机制在很大程度上尚未探索。该项目研究了生命前六个月内内分泌发育和身体生长之间的关系，这段时间以前被证明是终身健康和福祉的重要发育窗口，使用非侵入性激素收集的新方法。本研究将评价：（1）性类固醇与身体激素水平之间的纵向模式和关系;（2）婴儿激素水平与出生后身体生长的关系;（3）环境因素，如喂养、疾病和母亲特征对性类固醇变化的影响。为了实现这些目标，将收集格鲁吉亚州亚特兰大36名健康婴儿的每周激素、每周两次人体测量和每日生物行为数据。这项研究首次纵向记录了婴儿出生至六个月大期间的性类固醇水平，为人类生长提供了一个主要缺失的数据集。这项研究的密集性质允许调查婴儿期身体生长可能有助于成年生殖功能和健康的机制。同时在婴儿期的躯体和内分泌措施将允许测试的理论预测的生活史理论和生殖生态学的影响，当地生态在塑造内分泌反应在发展过程中。这些数据扩展了生命史理论的当前领域，通过检查生命史理论的定律，如能量分配和表型可塑性，转化为正常生长的婴儿的生理学。在实践层面上，本研究的结果将有助于公共卫生干预，旨在改善发达国家和发展中国家的婴儿生长。本研究中用于激素发育纵向研究的新型收集和提取方法可能在婴儿和儿童生长研究中具有更大规模的公共卫生和临床应用。此外，非侵入性和潜在的现场稳定协议，可以让研究人员扩展婴儿生长和发育的机制研究，以其他非西方人口，允许阐明改变这些人口的增长率的机制。在美国和世界范围内婴儿和儿童肥胖症的发病率不断上升，以及人们越来越关注儿童肥胖是否会导致早熟，成年发病率增加以及发生生殖系统癌症的风险中，这种机制的关注至关重要。

Recent epidemiological studies have highlighted the importance of fetal and infant development for lifelong physiology and health. While infant growth rates have been theorized to act in a programmatic manner determining future physiological function and adult chronic disease risk, intensive longitudinal investigations of infant somatic growth are rare and the relationship between somatic growth and the hormonal development underlying this growth are not well understood. Indeed, infancy is a sensitive period during which the tempo of growth and development is shaped in response to salient environmental variables. This shaping is mediated by the endocrine system, but the underlying mechanisms remain largely unexplored. This project examines the relationship between endocrine development and somatic growth during the first six months of life, a time previously documented to be an important developmental window for lifelong health and well-being, using novel methods of non-invasive hormonal collection. This study will evaluate: (1) the longitudinal patterns and relationship between sex steroids and somatic hormone levels; (2) the relationship between infant hormonal levels and postnatal body growth; and (3) the effects of environmental factors, such as feeding, illness and maternal characteristics on variations in sex steroids. To address these aims, weekly hormonal, twice weekly anthropometric and daily biobehavioral data will be collected on 36 healthy infants in Atlanta, Georgia.This research provides the first longitudinal documentation of infant sex steroid levels between birth and six months of age, contributing a major missing dataset in human growth. The intensive nature of the study permits investigation of the mechanisms by which body growth during infancy may contribute to adult reproductive function and health. Simultaneous somatic and endocrine measures during infancy will allow testing of the theoretical predictions of life history theory and reproductive ecology regarding the effects of local ecologies in shaping endocrine responses during development. These data expand the current realm of life history theory by examining the translation of the laws of life history theory, such as energy allocation and phenotypic plasticity, into the physiology of the normally growing infant.On a practical level, the results of this study will contribute to public health interventions aimed at improving infant growth in both developed and developing nations. The novel collection and extraction methods being used in this study for longitudinal investigation of hormonal development may have larger scale public health and clinical applications for the study of infant and child growth. Additionally, the non-invasive, and potentially field stable protocol, may allow researchers to extend mechanistic studies of infant growth and development to other non-Western populations, allowing elucidation of the mechanisms altering rates of growth in these populations. This mechanistic focus is critical amidst the rising incidence of infant and childhood obesity in the United States and worldwide and the growing concern over whether childhood obesity contributes to early maturation, increased adult morbidity, and the risk of developing reproductive cancers.