Estrogen in the etiopathogenesis of BPH

BACKGROUND. While the androgen-dependence of the prostate gland has long be en accepted, the participation of estrogen, mediated via the stroma in the elicitation of benign prostatic hyperplasia (BPH), has only recently been r ecognized. Its mode of action is still uncertain. METHODS. This review first outlines the regulation of gene expression via h ormones, growth factors, and other ligands in the coordination of cell grow th, differentiation, and function. Focus is next directed to factors partic ularly involved in phosphorylation of estrogen receptors. Then, the access of sex steroids, especially of estrogen to the cell and to the transduction machinery, is described, preparatory to examining the hypotheses by which this access causes the process of BPH to occur. RESULTS. It becomes clear that the necessary phosphorylative activities whi ch transmit signals to nuclear receptors and thence transcription of target genes can be performed by steroids or mimicked by proxy molecules and by c ross-talk between discrete pathways. The character and concentration of the available estrogen are determined by the extent of its biosynthesis, its p enetration of the cell, and its subsequent metabolism. In addition, the est rogen affects its own access through stimulation of facilitating peptide ho rmones, prolactin, and sex hormone-binding globulin. Finally, the induction of BPH is shown to be determined by the androgen/estrogen ratio and the ch ange in stromal/epithelial balance accompanying aging. CONCLUSIONS. Despite a growing knowledge of hormone levels, metabolism, and activities in the prostate, and the variety of processes and factors they affect, our explanation of BPH is still fanciful. (C) 1999 Wiley-Liss, Inc.