Objective: To study the relationship of the clinical parameters like lower urinary tract symptoms and erectile dysfunction with testosterone and the effect of testosterone replacement therapy on the clinical and biochemical parameters.

Materials and Methods: Thirty two patients with a serum total testosterone (TT) level under 319 ng/dl who applied to the Urology Outpatient Department of Firat University Hospital due to erectile dysfunction and loss of libido in a 24 months period are enrolled in the study. The patients have filled the AMS-Q (Aging Male Symptoms Questionnaire), the IIEF (International Index of Erectile Function) and the IPSS (International Prostate Symptom Score) questionnaire. The routine biochemical tests like luteinising hormone (LH), prolactine (PRL), progesterone (PG), total testosterone (TT), sex hormone binding globuline (SHBG), dehydroepiandrostenadionsulfate (DHEA-S) and albumin levels which are releated with erectile dysfunction and loss of libido are performed, the lipid profile is measured, free testosterone (fT) and bioavailable testosterone (Biot) levels were calculated by using TT, SHBG and albumin levels.

Results: There was a statistically significant relation between age, IPSS (p=0.0383) and SHBG (p= 0.04), between age Qmax (p=0.002), Qave (p=0.001) and Biot (p=0.028). Between before and after treatment results of IIEF, Qave, Qmax and the testosterone forms there was a statistically significant relation in a positive and AMS, PMR and LH results in a negative way. A positive statistically significant relationship between IIEF scores, fT and Biot is detected.

Conclusion: The results show that hypogonadism may occur in aging males due to the decrease of number and function of the leydig cells and loss of the diurnal pattern of testosterone. The symptoms can be evaluated with the questionnaire IIEF, AMS and IPSS. Our results show that some of the symptoms could be eliminated with testosterone replacement therapy.