The structural pervasiveness of estrogenic activity.

A remarkably wide variety of chemical structures, produced both by nature and by man, have estrogenic activity. While the molecular details of this structural perva? siveness of estrogenic activity are not known, it is less surprising if one considers that assays for estrogenic activity are extremely sensitive and can operate over a potency range of 10 million, that most estrogens share the common structural motif of a phenol or the functional equiva? lent of a phenol, and that most estrogens are lipophilic and thus can be resistant to metabolism and undergo bioconcentration. Evaluating the effect and potential risk of this structurally pervasive estrogenic activ? ity is a complex issue, and a number of factors should be considered: a) while excessive and aberrant exposure of humans and animals to estrogens may be detrimen? tal, a certain degree of exposure to natural estrogens from both endogenous and exogenous natural sources is unavoidable; b) estrogens from various sources may have beneficial as well as undesirable effects; c) their action may be selective on certain target sites; and d) they may have other nonestrogenic toxic or beneficial effects. Thus, one must be aware of the widespread potential for compounds to have estrogenic activity, and one must evaluate individually whether the activity of each of these estro? genic substances and our exposure to