Speaker: Robert Rountree. Describes the several types of estrogens: estrone, estradiol and estriol, how they are made in the body and their physiologic effects. Estrogen has a wide range of effects on the body, which are mediated by estrogen receptors and sex hormone binding globulin (SHBG). Details of estrogen metabolism and excretion round out the picture of this very powerful hormone. Xenoestrogens are a diverse group of environmental chemicals which can mimic the effects of estrogen in the body. Research is presented on their potential health effects due to disruption of the endocrine system.  The breast cancer connection is discussed in depth. Phytoestrogens are plant substances having significant physiologic effects on humans similar to those induced by endogenous estrogens. The most common classes of phytoestrogens are presented, with representative herbs and foods in each class. Effect on human health is discussed, and the interaction of phytoestrogens and xenoestrogens is explored.