PRL and hyperprolactinemia: Experimentally induced systemic hyperprolactinemia (excess of circulating prolactin [PRL]) in rats (Van Coppenolle et al., 2001) and in mice (Wennbo et al., 1997) results in drastic prostate hypertrophy exhibiting features of human BPH such as epithelium hyperplasia and increased stromal cellularity.