Getting the problem of endocrine disruption into focus: the need for a pause for thought.

The study of chemically-induced endocrine disruption in mammals is a relatively new field of endeavour, and it has been assailed by an unusual level of disagreement among investigators regarding the developmental effects produced by chemicals in animals. This article discusses the several sources of uncertainty in endocrine toxicity studies, and the intrinsic variability of many of the key experimental parameters. It is concluded that current uncertainties are due to the absence of an extensive agreed control database for the developmental parameters under study, coupled to the established intrinsic variability of these parameters between strains/species of test animals and test protocols. Only when these factors are generally accepted and well studied will it be possible to design studies capable of distinguishing the possible subtle endocrine toxicity of chemicals and chance observations that cannot be independently reproduced.