LAUSR

Abstract Estrone sulfate (E1S) is the most abundant circulating estrogen and it has the potential to be used as a biomarker in certain conditions where estimation of low levels of estrogen or changes in relative levels of estrogens are important. This review will critically consider the role of estimating E1S for clinical laboratory practice. As E1S is an estrogen, a wider discussion of estrogens is included to contextualize the review. Assays have been available for a number of years for these estrogens and they have been measured in a number of clinical research studies. However, E1S remains a rarely ordered test. This review highlights the literature that suggests the possible advantages of measuring E1S in addition to, or possibly in place of, the more commonly measured estradiol (E2) and the less commonly measured estrone (E1). The potential biomarker role of E1S in risk stratification for breast cancer, in promotion of proliferation of endometrial cancer, in prognostic information in advanced prostatic carcinoma, and in the monitoring of response to certain hormonal therapy for malignancy is discussed. The methods available for the measurement of E1S are reviewed and the limitations of the current methodologies are described. In conclusion, E1S has some interesting potential applications in clinical laboratory medicine that require further investigation.