Aim of present study is to assess, for the first time in literature, changes in pressure flow study (PFS) and changes in molecular profile of prostatic tissue (inflammatory and tissue remodeling markers) in men treated for 12 weeks with tadalafil 5 mg compared with placebo and to correlate these data with changes in symptoms scores (IPSS, International Prostatic Symptoms Score) in men with LUTS secondary to BPH refractory to alpha blockers.