Workshop to identify critical windows of exposure for children's health: Reproductive health in children and adolescents work group summary

This work group report addresses the central question: What are the critica l windows during development (preconception through puberty) when exposure to xenobiotics may have the greatest adverse impact on subsequent reproduct ive health? The reproductive system develops in stages, with sex-specific o rganogenesis occurring prenatally and further maturational events occurring in the perinatal period and at puberty. Complex endocrine signals as well as other regulatory factors (genetics, growth factors) are involved at all stages. Evidence from animal models and human studies indicates that many s pecific events can be perturbed by a variety of toxicants, with endocrine-m ediated mechanisms being the more widely studied. Prioritized research need s include basic studies on the cellular-molecular and endocrine regulation of sexual differentiation and development; increased efforts regarding pote ntial adverse effects on development in females, including breast developme nt; expanded animal studies on different classes of chemicals, comparing re sponses during development (prenatal and postnatal) with responses in adult s; and, more extensive explorations regarding the reproductive biology and toxicology of puberty in humans.