Reproductive hormones exert their effects at many life stages. During embryo and fetus development in the womb, these hormones direct formation of sex organs and the cells that give rise to sperm and eggs. They also determine the start of puberty, labor and lactation.

Reproductive hormones, including steroids (such as estrogens and androgens) and other regulatory hormones produced by the brain and pituitary gland, can be sensitive to environmental chemicals. EPA researchers conduct studies to determine how exposure during fetal or early postnatal development affects reproductive health later in life. Researchers are also working to figure out how these effects can be determined using molecular endpoints as early predictive tools.

In developing animals, EPA researchers are discovering biological indicators that will help scientists predict the effects of chemicals on reproductive health. One study examines the response of the hypothalamus, a hormone-rich region of the brain, to chemicals that shift the timing of the beginning of puberty. Researchers are also performing simple tests in cells that can streamline the assessment of potential endocrine disruptors.

Another study examines the response of hormone-producing brain cells to various chemicals and compares that response with effects in the adult animal. Researchers are working to see if chemicals change how hormones are produced and whether those changes result in adverse health outcomes. Other studies are examining how maternal stress (both chemically induced and non-chemically induced) and other prenatal exposures can impact the developing offspring (long-term effects).