Recent insights into the varying activity of estrogens.

Recent advances have added substantially to our understanding of the biology of estrogens. Estrogens are no longer considered to differ only in potency. Two estrogens can have similar effects in one tissue and very different effects in another. Additionally, an estrogen can have different effects in different tissues. It is now recognized that there are at least two estrogen receptors, ER-alpha and ER-beta, and that it is quite likely that estrogens also work through non-genomic mechanisms. The development of new methods of chromatographic separation has aided substantially in our ability to characterize the composition of Premarin, including the identification of estradiene, the fourth-most abundant estrogen in Premarin. Recent studies have contributed to our understanding of the unique profile of Delta(8,9) dehydroestrone sulfate, another of the Premarin estrogens. It was found that Delta(8,9) dehydroestrone sulfate is an active estrogen with a distinct pharmacological profile that results in significant clinical activity in vasomotor, neuroendocrine and bone preservation parameters. However, it displayed little or no efficacy, at the dose studied, on other peripheral parameters normally affected by classical estrogens. Increasing knowledge of the unique profiles of the Premarin components, as well as their complex interaction, will help to increase our understanding of the clinical profile of Premarin.