Academic journal article Environmental Health Perspectives

Biomarkers for Assessing Reproductive Development and Health: Part 1-Pubertal Development

Academic journal article Environmental Health Perspectives

Biomarkers for Assessing Reproductive Development and Health: Part 1-Pubertal Development

Article excerpt

The proposed National Children's Study has helped raise awareness of the issues related to children's health and the importance of monitoring the growth and development of children from preconception through adulthood. Many genetic predispositions can adversely impact the normal development process, and various environmental exposures have been linked to adverse reproductive health in rodent models and a small number of accidental human exposures. To monitor reproductive health and identify adverse effects at the earliest possible juncture, investigators must develop a network of biomarkers coveting all stages and aspects of reproductive development and function. Biomarkers are biological indicators that can be measured repeatedly and are informative on one or more aspects of biological development or function. They can range from the anatomical level down to the molecular level and may provide information on the nature of an exposure, the effect of an exposure, or the susceptibility of individuals or populations to the toxic effects of an exposure. In theory, biomarkers can be used to monitor a wide variety of conditions and responses ranging from abnormal development to early indicators of late-onset disease. The main stumbling block with this theory has been finding appropriate biomarkers for particular conditions and exposures. Such biomarkers must be easily accessible, robust, and sensitive. Ideally, they will be expressed across a large section of the population, and can be monitored quickly, easily, conveniently, and with minimal cost. In this review, we discuss some of the current and emerging biomarkers of human pubertal development. Key words: biomarker, development, human, longitudinal cohort study, puberty.

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A recent surge of reports from pediatricians in industrialized countries indicates that many girls are presenting with secondary sex characteristics at a younger age than has previously been considered normal (Herman-Giddens et al. 1997, 2001; Papadimitriou 2001). For example, current medical texts generally state that only 1% of girls show signs of puberty (breast development or growth of pubic hair) before 8 years of age. However, a study by Herman-Giddens et al. (1997) indicates that a substantial portion of American girls are presenting with one or both of these characteristics by age seven, and that 1% of girls have one or both of these pubertal markers by age three. Studies have also shown that the rate of growth for children and adolescents in the United States and other countries is significantly greater than in previous years (Freedman et al. 2000; Karpati et al. 2002). Some countries have even recorded an overall increase in final height (Padez 2002), although a recent review on the phenomenon concluded that the trends in final height and pubertal development are not strongly connected and that more longitudinal studies are needed for investigators to understand the short- and long-term consequences of the trends before we can interpret their importance (Karlberg 2002).

The phenomena of earlier puberty and increased final height have commonly been referred to as "the secular trend in growth." It is believed that the trend may have been in place for as many as 150 years in certain parts of the world (Samaras and Storms 2002), and it has been attributed largely to better child care--primarily as a result of improved nutrition, increased food supply, and improved health and sanitation services. A second hypothesis is that in some cases the mechanism of precocious puberty might involve environmental exposure to estrogenic endocrine disruptors (Teilmann et al. 2002). This has been suggested after studies indicating that a relatively high proportion of children (primarily girls) who have emigrated from developing to developed countries suffer precocious puberty and that their blood serum contains elevated levels of estrogenic pesticides (Krstevska-Konstantinova et al. …

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