The long term objective of this project is to develop better methods for the prevention and treatment of lower urinary tract symptoms (LUTS) in men. Benign prostatic hyperplasia (BPH) occurs in a vast majority of men and contributes to the morbidity known as LUTS. Clinical treatment for LUTS ascribed to BPH in men is a significant cost in healthcare, adversely affecting quality of life, and contribute to the mortality risk in men and women. While the etiology of BPH remains largely unclear available data are consistent with the hypothesis that changing hormone levels, especially testosterone (T) and estradiol-17b (E2), are underlying causes of BPH and bladder outlet obstruction (BOO). In support of this idea the standard of care for men with enlarged prostates targets the androgenic pathway. However, as men age the amount of androgens significantly decrease while the estrogen to testosterone ratio increases. This posits that estrogens may be an important pathway in the manifestation or maintenance of BPH and associated BOO. New unpublished data from us and others implicates the testosterone metabolite E2 as a key mediator of BPH. However, little is known how estrogens may elicit their affects in the prostate and few models of BPH and BOO exist that will allow for the genetic and pharmacologic dissection of molecular pathways. In this regard, we have developed a new genetically tractable mouse model in which males treated with T+E2, to mimic the hormonal milieu in aging men, develop lower urogenital tract abnormalities consistent with BPH found in men. These criteria include: new glandular prostatic growth, prostatic urethral narrowing, progressively enlarged bladders, and urination patterns of high frequency and low volume. Our preliminary data implicate E2/estrogen receptor (ER)-signaling and specifically ER-a/a homodimerization as a key molecular determinant of lower urogenital tract abnormalities that are consistently found in men with BPH. Furthermore, we have observed increased expression of fibroblast growth factors (FGFs) and activated FGF receptors in human specimens of BPH and in our animal models. We hypothesize that abnormalities within the lower urogenital tract are mediated by inappropriate E2/ER-signaling in turn affecting paracrine acting estromedins to promote BPH and associated BOO.