The relationship between hypogonadism and erectile dysfunction.

It is well known that testosterone enhances sexual interest leading to an increased frequency of sexual acts and an increase in the frequency of sleep-related erections. However, it has little effect on fantasy- or visually induced erections. Exact contribution to erection from testosterone in men remains unclear. Animal studies have well demonstrated that testosterone plays critical physiological (activity of nitric oxide synthases and phosphodiesterases), biochemical (through an endothelial-independent pathway and adrenergic tonicity) and structural (change of fibroelasticity and hollow cell accumulation) roles in erectile function. The supplementation of testosterone to castrated animals can restore erectile function. Clinically, reports of patients with erectile dysfunction (ED) combined with hypogonadism who receive testosterone therapy have inconsistent results. However, testosterone may ameliorate the expression of the phosphodiesterase-5 (PDE5) inhibitor, and the use of testosterone in conjunction with the PDE5 inhibitor revealed convincing results. Because of potential risks in clinical use, testosterone therapy should be individualized, carefully considered and closely monitored, especially, in patients with possible occult prostate cancer, and large benign prostatic hyperplasia. Lower urinary tract symptoms might be worsened by this treatment, since the prostate is an androgen-dependent tissue.