Benign prostatic hyperplasia: pathogenesis and the role of medical management

Natural potent androgens: lessons from human genetic models

Male pseudohermaphroditism due to 17 beta-hydroxysteroid dehydrogenase-3 (17 beta-HSD-3) deficiency and 5 alpha-reductase-2 (5 alpha-RD-2) deficiency provides natural human genetic models to elucidate androgen actions. To date, five 17 beta-HSD isozymes have been cloned that catalyse the oxidoreduction of androstenedione and testosterone and dihydrotestosterone (DHT), oestrone and oestradiol. Mutations in the isozyme 17 beta-HSD-3 gene are responsible for male pseudohermaphroditism due to 17 beta-HSD deficiency. The type 3 isozyme preferentially catalyses the reduction of androstenedione to testosterone and is primarily expressed in the testes. Fourteen mutations in the 17 beta-HSD-3 gene have been identified from different ethnic groups. Affected males with the 17 beta-HSD-3 gene defect have normal wolffian structures but ambiguous external genitalia at birth. Many are raised as girls but virilize at the time of puberty and adopt a male gender role. Some develop gynaecomastia at puberty, which appears to be related to the testosterone/oestradiol ratio. Two 5 alpha-reductase (5 alpha-RD) isozymes, types 1 and 2, have been identified, which convert testosterone to the more potent androgen DHT. Mutations in the 5 alpha-RD-2 gene cause male pseudohermaphroditism, and 31 mutations in the 5 alpha-RD-2 gene have been reported from various ethnic groups. Such individuals also have normal wolffian structure but ambiguous external genitalia at birth and are raised as girls. Virilization occurs at puberty, often with a gender role change. The prostate remains infantile and facial hair is decreased. Balding has not been reported.

Prostate cancer

Prostate cancer is the most common noncutaneous malignancy diagnosed in American men, and in 1994 it will pass lung cancer as the most common cancer diagnosed in the United States, with an estimated 200,000 new cases. The molecular biology of prostate carcinogenesis is rapidly advancing, and it is clear that, to a degree, prostate cancer is a heritable disease. The use of serum prostate-specific antigen (PSA) as a screening tool has been widely accepted by the medical community, although the evidence to support the efficacy of screening is not yet available. The curative approaches to organ-confined, clinically localized prostate cancer include radiation therapy, radical prostatectomy, and close observation in selected patients. The absence of well-designed clinical trials contributes to the confusion surrounding which curative treatment is the best option in individual patients. The standard approach to patients with evidence of extracapsular spread without distant metastases has been external-beam radiotherapy, although the results with radiation therapy alone in these patients has left considerable room for improvement. Innovative combined-modality approaches are currently being investigated at a number of institutions for these poor-prognosis patients. Three-dimensional conformal radiation therapy is currently being investigated at multiple institutions and offers some hope for improved results. The treatment of metastatic disease remains hormonal manipulation, although the exact nature of optimal androgen deprivation is currently a matter of considerable debate. In patients with hormone-refractory disease newer regimens using novel chemotherapy regimens offer some promise.

Review of the role of androgenic hormones in the epidemiology of benign prostatic hyperplasia and prostate cancer

OBJECTIVE

Examine current knowledge and concepts on the role of androgenic hormones in the epidemiology of benign prostatic hyperplasia (BPH) and prostate cancer (PCa).

METHODS

Review of the clinical and scientific literature on normal androgen physiology, hormonal physiology of BPH and PCa tissue, serum hormone levels in patients with BPH or PCa, and the correlation between serum and tissue androgenic hormones.

RESULTS

BPH and PCa are enormous clinical problems for our health care system; profound changes in the clinical aspects of these diseases are evident in recent years. Early identification or prevention are realistic goals; identification of higher risk groups would be extremely valuable. Androgen stimulation of the prostate is likely to be important in the promotion of BPH or PCa. Tissue hormone measurements have not identified substantial differences in hormone levels, but precise pathologic control of the tissue examined is suspect. Examinations of serum hormone levels in disease states have produced conflicting results, but the presence or absence of BPH or PCa was often based on imprecise clinical observations, making interpretation difficult. There are minimal data confirming that the serum hormones measured previously actually reflect intraprostatic tissue activity.

CONCLUSIONS

The value of serum hormone measurements to identify higher risk groups for BPH or PCa is an area of continuing uncertainty because of substantial flaws in the design of many previous studies based on a failure both to define the presence or absence of BPH or PCa precisely in patients studied and measure the appropriate androgen metabolites. Similarly, it is not possible reliably to implicate differences in androgenic stimulation as a cause for racial differences in PCa. The ability of serum hormone levels to correlate with prostatic tissue androgenic stimulation has not been evaluated. Additional research in the relationships between androgenic stimulation and the development of clinically significant BPH or PCa is needed.