Binding Protein 3 (IGF-I) and IGF-I Receptor Genes and with an Increase in IGF Associated with Suppression of Insulin-like Growth Factor I Reduction of Ventral Prostate Weight by Finasteride Is

Finasteride, a competitive and specific inhibitor of 5a-reductase, is widely used in the treatment ofsymptomatic benign prostatic hyperplasia. We demonstrate here that finasteride, when administered in an in vivo experimental system, caused ventral prostate regression. Intraprostatic dihydrotestosterone leveis decreased, whereas testosterone levels in creased in a dose-dependent manner following finasteride treatment. Fin asteride also inhibited the expression of insulin-like growth factor (IGF)-I and IGF-I receptor genes in the ventral prostate. Finasteride significantly increased IGF binding protein-3 and slightly decreased IGF binding protein-2, -4, and -5 gene expression. Because IGFs are potent mitogens for prostate epithelial cells, this newly described activity of flnasteride may contribute to its antiproliferative properties, particularly with regard to the inhibition of prostate growth seen clinically and in animal modeis.