Changes in dihydrotestosterone metabolism and the development of benign prostatic hyperplasia in the aging beagle

Previous studies have demonstrated that the 2-3--fold abnormal elevation in prostatic dihydrotestosterone (DHT) content characteristically associated with canine benign prostatic hyperplasia (BPH) is due to a shift in the overall balance in the complex metabolism of DHT in the gland itself [1, 2]. Since the incidence of canine BPH increases with host age [3], the question arises as to whether the characteristic shift in DHT metabolism is associated with the general process of aging or with the specific development of BPH. To resolve this issue, the activities of prostatic androgen metabolism were quantitatively assayed in prostatic tissue from a large series of age-matched normal and BPH dogs ranging in age from 0.7-9.0 years. These analyses revealed that, regardless of the age of the host, there is a consistent statistical increase in several of the activities which produce DHT (i.e. 5 alpha-reductase, 3 alpha-HSOR oxidase, and 17 beta-HSOR reductase) without a concomitant increase in any of the activities which remove this steroid in BPH as compared to age-matched normal prostatic tissue. These results suggest that in canine BPH tissue the characteristic changes in DHT metabolism which increase the tissue's ability for net formation of DHT are specifically associated with the development of BPH itself and not due simply to the general process of aging per se.     

Role of inflammation in benign prostatic hyperplasia

Inflammation of the prostate may represent a mechanism for hyperplastic changes to occur in the prostate. There are a variety of growth factors and cytokines that may lead to a proinflammatory process within the prostate. There are several proposed mechanisms that lead to both the intrinsic and extrinsic basis of inflammation. Prostatic inflammation may represent an important factor in influencing prostatic growth and progression of symptoms. This article reviews the recent literature on inflammation leading to chronic prostatic diseases, such as benign prostatic hyperplasia.     

Medical treatment of benign prostatic hyperplasia

Medical therapy for the treatment of benign prostatic hyperplasia (BPH) became an accepted standard of care in the 1990s following the reports of randomized, double-blind, placebo-controlled studies showing that finasteride, a 5-α reductase inhibitor, and terazosin, an α-blocker, significantly improved lower urinary tract symptoms and increased peak urinary flow rates in men with BPH. This article reviews novel approaches to the pharmacological treatment of BPH.     

Clinical evaluation of benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) is the most common neoplastic condition afflicting men and constitutes a major factor impacting male health. Clinical evaluation to assess the presence and degree of voiding dysfunction and/or the role of BPH in its presence has an increasingly broad spectrum of treatment goals. The goals of the evaluation of such men are to identify the patient's voiding or, more appropriately, urinary tract problems, both symptomatic and physiologic; to establish the etiologic role of BPH in these problems; to evaluate the necessity for and probability of success and risks of various therapeutic approaches; and to present the results of these assessments to the patient so he can make an informed decision about management recommendations and available alternatives.     

Urinary hormone excretion in benign prostatic hyperplasia

The urinary excretion of LH, low polar oestrogens (oestrone + oestradiol-17β), dehydroepiandrosterone, androsteone, aetiocholanolone, pregnanediol and total 17-keto-and 17-ketogenic steroids has been determined in 30 men aged 60–84 years with benign prostatic hyperplasia and in 39 healthy men aged 60–79 years. The results show a significantly elevated oestrogen excretion in benign prostatic hyperplasia as compared with the control group. No other significant differences were found in the urinary hormone excretion. It is speculated that the increased oestrogen levels might stimulate the prostate growth mainly by facilitating the transport of peripheral testosterone into prostate cell.     

Pharmacotherapy for benign prostatic hyperplasia.

Benign prostatic hyperplasia is a benign neoplasm of the prostate seen in men of advancing age. Microscopic evidence of the disorder is seen in about 70% of men by 70 years of age, whereas symptoms requiring some form of surgical intervention occur in 30% of men during their lifetime. Although the exact cause of benign prostatic hyperplasia is not clear, it is well recognized that high levels of intraprostatic androgens are required for the maintenance of prostatic growth. In recent years, extensive surveys of patients undergoing transurethral resection of the prostate reveal an 18% incidence of morbidity that has essentially not changed in the past 30 years. This procedure is also the second highest reimbursed surgical therapy under Medicare. These findings have resulted in an intensive search for alternative therapies for prostatic hyperplasia. An alternative that has now been well defined is the use of alpha-adrenergic blockers to relax the prostatic urethra. This is based on findings that a major component of benign prostatic hyperplasia symptoms is spasm of the prostatic urethra and bladder neck, which is mediated by the alpha-adrenergic nerves. A second approach is to block androgens involved in maintaining prostate growth. Several such drugs are now available for clinical use, and we discuss their side effects and use. We also include the newer recommendations on evaluating benign prostatic hyperplasia that are cost-effective yet comprehensive.     

Evaluating men with benign prostatic hyperplasia

The clinical manifestations of benign prostatic hyperplasia (BPH) include lower urinary tract symptoms (LUTS), poor bladder emptying, urinary retention, detrusor instability, urinary tract infection, hematuria, and renal insufficiency. However, the majority of men with BPH present with LUTS only. Because LUTS can indicate a variety of conditions, evaluation of symptomatic men must first aim to identify or exclude BPH and, if present, assess its severity. It is important to assess symptom severity at baseline and during follow-up, using the American Urological Association Symptom Index or the International Prostate Symptom Score. Further testing can then be tailored to narrow the diagnosis and guide treatment decisions. Factors such as patient age and concomitant malignancy will also affect management, but the main goal of treatment remains the improvement of quality of life for the patient.     

Prostate development and growth in benign prostatic hyperplasia

The etiology of benign prostatic hyperplasia [BPH] in elderly men has intrigued anatomists, pathologists and scientists for centuries. Studies of morbid anatomy, clinical observations and contemporary cellular biology have contributed to an evolving interpretation of the causality of the disease. Insights into the detailed microanatomy and ductal architecture of the prostate during stages of fetal and early postnatal development suggest that mechanisms involved in the early growth period become aberrantly expressed in elderly men. Age, hormones and epithelial-mesenchymal interactions are all contributing factors to the pathogenesis of BPH. Control of the microenvironment in normal and abnormal growth is a multifactorial process. Susceptibility to the disease may include clinical comorbid diseases, region-specific changes in cell-cell interactions and a variety of signaling pathways including a novel hypothesis regarding the role of the primary cilium as a regulator of signal transduction mechanisms. Recent work in animal models has shown that there are region-specific differences within the prostate that may be significant because of the dynamic and intricate interplay between the epithelium and mesenchyme. Because of the focal nature of BPH a closer examination of normal morphogenesis patterns, which defines the gland's architecture, may facilitate a detailed understanding of the atypical growth patterns.     

Alpha blockers for the treatment of benign prostatic hyperplasia

The evolution of alpha blocker therapy for benign prostatic hyperplasia (BPH) has focused on improving convenience and tolerability. Indications for treating BPH include reversing signs and symptoms or preventing progression of the disease. The indication that most commonly drives the need for intervention is relief of lower urinary tract symptoms (LUTS) with the intent of improving quality of life. Alpha blockers are the most effective, least costly, and best tolerated of the drugs for relieving LUTS. Four long-acting alpha 1 blockers are approved by the Food and Drug Administration for treatment of symptomatic LUTS/BPH: terazosin, doxazosin, tamsulosin, and alfuzosin. All are well tolerated and have comparable dose-dependent effectiveness. Tamsulosin and alfuzosin SR do not require dose titration. Alfuzosin, terazosin, and doxazosin have all been shown to be effective in relieving LUTS/BPH independent of prostate size.     

Relationship between the prostatic tissue components and natural history of benign prostatic hyperplasia

OBJECTIVE: Few reports have been published on the relationship between prostatic tissue components and the natural history of benign prostatic hyperplasia (BPH). The present study was undertaken to evaluate this relationship. STUDY DESIGN: Forty-nine patients with BPH who underwent suprapubic prostatectomy were studied. Six infant prostates and 10 non-BPH specimens were obtained from autopsy. Specimens were stained with antibodies to alpha-smooth muscle actin, and the mean ratio of the stroma was determined with computer image analysis. Stromal ratios were evaluated according to resected prostate weight and age. RESULTS: The stroma comprised 82.6 +/- 8.4% of the prostate area at 0-1 year of age and 43.7 +/- 5.1% at 15-28 years of age. In BPH, the stromal proportion increased to 55.9 +/- 10.2%, but decreased with increases in prostate weight and/or age. CONCLUSION: The stromal component increased in patients with BPH and decreased with increased prostate weight and/or age, comprising approximately 42-47% of the prostate area, as in the non-BPH prostate, indicating a balance in prostatic tissue components in both patients with BPH and the non-BPH prostate.     

Estradiol- and estriol-binding in human benign prostatic hyperplasia.

Binding of the natural estrogens, estradiol and estriol, was investigated, in 34 samples of human benign prostatic hypertrophy (BPH) tissue, using Scatchard analysis and agar gel electrophoresis. Saturation binding analysis using a wide range of concentrations of both ligands resulted in curvilinear Scatchard plots. This confirmed the presence of two binding forms for estradiol: a true estrogen receptor, and a protein with lower affinity and higher capacity. Both binding species were also demonstrated and quantified with estriol. The electrophoretic process, after incubation at low and high ligand concentrations also resulted in separation, for both estrogens, of two binding peaks. They are probably two distinct forms of the low affinity, high capacity binding measured by Scatchard. The procedure used in our laboratory was not able to provide accurate determination of the concentrations of these binding forms. Possible modifications to alleviate these drawbacks are discussed.     

Etiological considerations for the growth of stroma in benign prostatic hyperplasia

The finding that human benign prostatic hyperplasia (BPH) consisted primarily of fibromuscular tissue has led to basic research into the hormonal control of the growth of male accessory sex organ smooth muscle. By using the separated epithelium and muscle layers of the guinea pig seminal vesicle, it was determined that the epithelium exhibited only reversible androgen-induced growths, whereas the muscle proved to be a target tissue for both androgen and estrogen, and exhibited irreversible growth responses. It was of particular interest that the normal androgen-dependent pubertal development of the muscle involved an approximate twofold increase in DNA, followed by the development of a complete and relatively selective androgenic insensitivity in this parameter. An understanding of the factors leading to this apparently normal androgen-dependent loss of the proliferative response in muscle may allow for the development of specific hypotheses for the reawakened stromal growth in BPH. Research on other organ systems focusing on the various factors and mechanisms involved in muscle growth regulation is briefly discussed.     

Landmark studies impacting the medical management of benign prostatic hyperplasia

The treatment of benign prostatic hyperplasia (BPH) has changed dramatically over the past 10 years. Phase 3 studies of the safety and effectiveness of alpha-blockers (eg, terazosin and doxazosin) and 5-alpha-reductase inhibitors (eg, finasteride) for the treatment of BPH began to appear in the literature in 1992. This article reviews the results of landmark studies of these agents, either separately as monotherapy or as combined therapy, for the treatment of BPH. The relationship between prostate size and lower urinary tract symptoms (LUTS) is discussed. Although prostate volume is not as strongly correlated with these symptoms as was once believed, it has been shown to be an important predictor of risk for developing acute urinary retention. alpha-Blockers represent an effective treatment for LUTS independent of prostate volume; the clinical benefit of finasteride for LUTS is limited primarily to men with large prostates. Finasteride decreases the risk of progression to acute urinary retention and the requirement for surgical intervention; this benefit is greatest in men with enlarged prostates.