A variety of chemicals have been found to affect the endocrine system, which in turn alter the hormonal balance of the exposed organism. It has been well established that fish are susceptible to endocrine disruption by estrogens and xenoestrogens (Sumpter and Jobling, 1995). Sublethal effects (e.g. reproductive toxicity) observed in fish exposed to environmental estrogens may be mediated via cell death stimulation.

Since the mid-nineteenth century, many observations have indicated that cell death plays an important role during physiological processes of multicellular organisms, particularly during embryogenesis and metamorphosis (Lockshin and Zakeri, 2001). The term programmed cell death means cell death during development is not of accidental nature but follows a sequence of controlled steps leading to locally and temporally defined self-destruction. Cell death is a critical part of life cycle along with growth and differentiation.