Then, 16 medium to low abundance proteins (DSG2, IL6ST, LAMP2, PLXNB2, GOLM1, CTSD, TIMP1, PTPRF, IGFBP3, ASPN, POSTN, APMAP, LAMP1, LCN2, PIGR, PEDF) were selected and quantified in duplicates by SRM on a cohort of 54 patients (PCa = 24 and BPH = 31). The gene discussed is CTSD; the disease is benign prostatic hyperplasia.