The importance of DHT in causing nodular hyperplasia is supported by clinical observations in which an inhibitor of 5α-reductase such as finasteride is given to men with this condition. Therapy with a 5α-reductase inhibitor markedly reduces the DHT content of the prostate and, in turn, reduces prostate volume and BPH symptoms.Testosterone promotes prostate cell proliferation, but relatively low levels of serum testosterone are found in patients with BPH. One small study has shown that medical castration lowers the serum and prostate hormone levels unevenly, having less effect on testosterone and dihydrotestosterone levels in the prostate.While there is some evidence that estrogen may play a role in the cause of BPH, this effect appears to be mediated mainly through local conversion of androgens to estrogen in the prostate tissue rather than a direct effect of estrogen itself. In canine in vivo studies castration, which significantly reduced androgen levels but left estrogen levels unchanged, caused significant atrophy of the prostate. Studies looking for a correlation between prostatic hyperplasia and serum estrogen levels in humans have generally shown none.In 2008, Gat et al. published evidence that BPH is caused by failure in the spermatic venous drainage system resulting in increased hydrostatic pressure and local testosterone levels elevated more than 100 fold above serum levels. If confirmed, this mechanism explains why serum androgen levels do not seem to correlate with BPH and why giving exogenous testosterone would not make much difference.
PDE also likely improves symptoms when used in combination with 5-alpha reductase inhibitors. Several phosphodiesterase-5 inhibitors are also effective, but may require multiple doses daily to maintain adequate urine flow. Tadalafil, a phosphodiesterase-5 inhibitor, was considered then rejected by NICE in the UK for the treatment of symptoms associated with BPH. In 2011, the U.S. Food and Drug Administration approved tadalafil to treat the signs and symptoms of benign prostatic hyperplasia, and for the treatment of BPH and erectile dysfunction (ED), when the conditions occur simultaneously. Others
Antimuscarinics such as tolterodine may also be used, especially in combination with alpha blockers. They act by decreasing acetylcholine effects on the smooth muscle of the bladder, thus helping control symptoms of an overactive bladder. Self-catheterization
Intermittent urinary catheterization is used to relieve the bladder in people with urinary retention. Self-catheterization is an option in BPH when it is difficult or impossible to completely empty the bladder. Urinary tract infection is the most common complication of intermittent catheterization. Several techniques and types of catheter are available, including sterile (single-use) and clean (multiple use) catheters, but, based on current information, none is superior to others in reducing the incidence of urinary tract infection. Surgery
If medical treatment is not effective, surgery may be performed. Surgical techniques used include the following:

Transurethral resection of the prostate (TURP): the gold standard. TURP is thought to be the most effective approach for improving urinary symptoms and urinary flow, however, this surgical procedure may be associated with complications in up to 20% of men.