Recent advances in clinical/molecular andrology

5alpha-reductase inhibitors in benign prostatic hyperplasia and prostate cancer risk reduction

Androgens play an essential role in prostatic development and function, but are also involved in prostate disease pathogenesis. The primary prostatic androgen, dihydrotestosterone (DHT), is synthesized from testosterone by 5alpha-reductase types 1 and 2. Inhibition of the 5alpha-reductase isoenzymes therefore has potential therapeutic benefit in prostate disease. The two currently approved 5alpha-reductase inhibitors (5ARIs), finasteride and dutasteride, have demonstrated long-term efficacy and safety in the treatment of benign prostatic hyperplasia. Finasteride, a type-2 5ARI, has also been studied for its ability to reduce the incidence of biopsy-detectable prostate cancer in the Prostate Cancer Prevention Trial. Treatment with dutasteride, a dual 5ARI, has been shown to result in a greater degree and consistency of DHT suppression compared with finasteride. Two large-scale studies of dutasteride are currently investigating the role of near-maximal DHT suppression in the settings of prostate cancer risk reduction and expectant management of localized prostate cancer.

Long-term therapy with the dual 5alpha-reductase inhibitor dutasteride is well tolerated in men with symptomatic benign prostatic hyperplasia

OBJECTIVE

To examine the long-term (4-year) safety and tolerability of dutasteride in the treatment of symptomatic benign prostatic hyperplasia (BPH).

PATIENTS AND METHODS

Patients who completed the double-blind phase of three dutasteride Phase III studies were eligible to enter a 2-year open-label extension, during which all patients received dutasteride 0.5 mg. Safety was assessed, including adverse-event reporting, clinical laboratory assessments, yearly physical examinations, and vital sign assessments.

RESULTS

In all, 2340 patients entered the open-label phase, 1188 of whom previously received dutasteride during the double-blind phase of the study. The most common drug-related adverse events (occurring in > or = 1%) were effects on sexual function, which decreased with a longer duration of therapy. Gynaecomastia was reported in a small percentage of men throughout the 4-year study period. The incidence of individual sexual functional adverse events that led to withdrawal was < or = 1% (0.3-1.0%) during the 4-year study period. Dutasteride had no relevant effects on vital signs or clinical laboratory variables.

CONCLUSION

These data show that dutasteride is well tolerated during long-term use for the treatment of symptomatic BPH.

Control of spermatogenesis in primate and prospect of male contraception

The present review is a summary of mechanisms of spermatogenesis in primates with emphasis on anti-spermatogenesis of testosterone (T), gossypol, and "testicular heat stress" for development of male contraception, Both FSH and testosterone stimulate all phases of spermatogenesis. FSH is capable of amplifying the population of the differential spermatogonia (B1, B2, B3 and B4) and controls the spermatogonia production rate, and, in synergy with testosterone, regulating spermatogenesis in adult monkeys. Pituitary FSH beta gene expression is governed by a feedback of Beta inhibin, which is a major component of the testicular negative feedback signals. Beta inhibin secreted by Sertoli cells is in turn inhibited by testosterone from Leydig cells under the control of LH. Disturbance of the normal interaction of pituitary FSH with Sertoli cell Beta inhibin is responsible for azoospermia or oligozoospermia induced by exogenous T. Three possible regimens of T, gossypol and "heat stress" have been suggested for male contraception. They act on different sites and stages of spermatogenesis in testis or sperm activity in epididymis. Apoptosis induced by testosterone occurs mainly at staged VII-VIII of spermatogenesis while that by testicular "heat stress" mostly occurs at stages I-IV and X-XII. Low dose of gossypol mainly influences the sperm activity in the epididymis although it also acts on testicular spermatids.

Safety and tolerability of the dual 5alpha-reductase inhibitor dutasteride in the treatment of benign prostatic hyperplasia

OBJECTIVE

The objective of this paper is to examine safety and tolerability data from a number of recently completed clinical trials with the novel, dual 5alpha-reductase inhibitor, dutasteride.

METHODS

Intent-to-treat analyses were conducted on data for dutasteride 0.5 mg/day for drug-related adverse events, clinical laboratory test results, and prostate-specific antigen (PSA) levels derived from four large, randomised, double-blind clinical trials (n=5655). Further data were derived from a randomised, double-blind combination study of dutasteride 0.5 mg/day and tamsulosin 0.4 mg/day (n=327), and several safety studies conducted in healthy volunteers.

RESULTS

Data from two-year blinded clinical studies demonstrate that dutasteride is well tolerated, with a profile comparable with that of placebo. The exception is a modestly elevated incidence of impotence, decreased libido, ejaculation disorders, and gynaecomastia. Clinical laboratory test abnormalities were reported by <1% of patients treated with dutasteride, and abnormal values occurred with similar frequency versus placebo-treated patients. In a healthy volunteer study, when dutasteride was administered daily for 1 year, it did not significantly affect bone metabolism markers, bone mineral density or lipid profiles. Dutasteride reduced total serum PSA concentrations by approximately 50% following 6, 12, and 24 months of treatment but had no effect on free-to-total PSA levels. The safety profile of dutasteride did not differ from that of finasteride in a large, parallel-group, comparator trial. Additionally, when dutasteride was used in combination with an alpha(1)-blocker, the drug-related adverse event profiles were as would be expected for the individual agents.

CONCLUSIONS

Considered together, these data demonstrate dutasteride to be well-tolerated.

Management of erectile dysfunction by combination therapy with testosterone and sildenafil in recipients of high-dose therapy for haematological malignancies

Erectile dysfunction (ED) is a well recognised complication of bone marrow transplantation, which affects quality of life in adult patients. Although the major contributory factors include hypogonadism and psychogenic factors, the best treatment still remains to be established due to the complex aetiopathology of the condition. Here, we report our preliminary results in eight patients treated with testosterone replacement therapy and sildenafil. We studied eight male recipients of BMT aged 22-58 years, presenting with clinical features of hypogonadism, ED, diminished libido and ejaculatory disorders. ED was assessed clinically and by colour flow Doppler studies of the cavernosal vessels. Testicular function was assessed by testicular volume, FSH, LH and testosterone (T) measurements. Erectile performance, libido and ejaculatory function were determined by a structured interview. Patients had severe primary hypogonadism as evidenced by low mean testicular volume, elevated gonadotrophins and low normal mean testosterone levels compared with controls. All had Leydig cell insufficiency (LCI) with or without frank serum testosterone insufficiency. All except one had cavernosal arterial insufficiency. All patients received intramuscular injections of testosterone cypionate (250 mg 4 weekly) for 6 months and 50-100 mg of sildenafil orally, one to two times per week. All patients responded favourably as substantiated from the NIH consensus criteria. Our preliminary results suggest that this combined therapy is a safe and effective therapeutic approach in recipients of high-dose therapy presenting with ED after transplant.

Gynaecomastia with hypergonadotrophic hypogonadism and Leydig cell insufficiency in recipients of high-dose chemotherapy or chemo-radiotherapy

Late side-effects of stem cell transplantation include hypogonadism with infertility and sexual dysfunction, but gynaecomastia is less well recognised. We report five cases of gynaecomastia with features of hypergonadotrophic hypogonadism (primary testicular failure), who received either a TBI/cyclophosphamide conditioned allograft (n = 3) or a BEAM autograft (n = 2). Patients receiving an allograft had gynaecomastia, Leydig cell insufficiency (LCI) diminished libido and erectile dysfunction. Surgery was required in one case, while in two cases the gynaecomastia resolved spontaneously after 6 months. Two patients also had gynaecomastia and sexual dysfunction, severe hypogonadism, very low testosterone levels and marked hyperprolactinaemia following autoBMT. Both responded well to testosterone replacement therapy (TRT). As a group, all patients had primary testicular failure and all except one, had LCI (compensated or frank). However, there was no correlation between the severity of gynaecomastia and the degree of endocrine dysfunction. This preliminary study is the first to suggest that gynaecomastia, due to primary hypogonadism and LCI, may be a significant complication of myeloablative conditioning therapy. Therefore gynaecomastia in BMT recipients must always be treated as a pathological entity as it may be the external manifestation of a complex endocrine pathology. It is a potentially treatable condition. Although spontaneously reversible, some patients may require TRT or even surgery. We recommend comprehensive endocrine testing in conjunction with a reproductive endocrinologist and prompt intervention to alleviate embarrassment and anxiety in afflicted BMT recipients.

Low plasma testosterone in varicocele patients with impotence and male infertility

To study the affect of bilateral varicocele (grade 3) on impotence and male infertility patients, 29 patients were selected from an outpatient clinic during 15 May 1998 to 15 August 1999 (the mean age was 33.9 +/- 6.3), 15 patients complaining of erectile dysfunction and 14 patients complaining of male infertility. The mean duration of impotence was 3 +/- 2.3 years and for male infertility was 6 +/- 2.5. All organic and psychogenic causes related to impotence and male infertility except bilateral varicocele (grade 3) and low plasma testosterone were excluded by clinical and laboratory investigations. Twenty males with normal erection and fertility were included as controls. Detailed medical history and complete physical examination included measurement of testicular size by orchiometer; semen and hormonal parameters were measured for all patients and control. In impotent patients left and right testicular volume was significantly decreased (p < .05), while in male infertility patients left and right testicular volume was highly significantly and, significantly decreased (p < .005, p < .05) compared to controls. In male infertility patients, left testicular volume was highly significantly decreased compared to impotent patients (p < .005). The sperm count and semen volume in impotent patients was significantly decreased (p < .05, p < .01), but no significant differences were found in sperm motility and abnormal forms, while in male infertility the sperm count was highly significantly decreased (p < .005), the sperm motility was significantly decreased (p < .05), the abnormal form was significantly increased (p) < .05), but in the semen volume there was no significant difference compared to controls. In impotent patients the sperm count was significantly increased and abnormal form was significantly decreased compared to male infertility (p < .05). The mean serum testosterone was significantly decreased in impotent patients (p < .01), and highly significantly decreased in male infertility (p < .005) compared to controls. The mean serum FSH was significantly increased in male infertility (p < .05) and nonsignificant in impotent patients compared to controls. The mean serum LH and prolactin levels were nonsignificant in both impotent and male infertility patients compared to controls, but LH was significantly increased in impotence compared to male infertility patients (p < .025). Therefore, bilateral varicocele (grade 3) is associated with significant reduction in testicular function with significant increase in serum levels of FSH and LH, which may cause erectile dysfunction and male infertility.

Cavernosal arterial insufficiency is a major component of erectile dysfunction in some recipients of high-dose chemotherapy/chemo-radiotherapy for haematological malignancies

We studied 24 male patients aged 26-62 years (median 41) prospectively presenting over a 5 year period with clinical features of hypogonadism and erectile dysfunction (ED), who had been treated with autologous or allogeneic bone marrow/stem cell transplant for a variety of haematological malignancies and had received either high-dose chemotherapy or high-dose chemotherapy combined with total body irradiation (TBI). Ten healthy adult controls (aged 35-50 years) were also studied. Erectile dysfunction (ED) was assessed clinically and by colour flow Doppler studies of the cavernosal vessels. Testicular function was assessed by testicular volume including orchidometry, FSH, LH and testosterone measurements. Libido and ejaculatory function were also recorded. Patients had severe hypogonadism as evidenced by low mean testicular volume (7.0 +/- 2.4 ml vs 20 +/- 2.0 ml; P < 0.001), elevated gonadotrophins (FSH = 18.54 +/- 7.61 vs 5 IU/l (P < 0.001); LH = 8.02 +/- 2.89 vs 3. 9 IU/l (P < 0.001)) and low normal mean testosterone levels (16.4 nmol/l +/- 9.1 vs 22.4 nmol/l (P < 0.5)). Cavernosal arterial insufficiency was found in 11/14 of TBI-treated and in 3/10 HDC-treated patients, indicative of vasculogenic damage to corpora cavernosal vessels. Patients were given a therapeutic trial with testosterone replacement therapy (TRT). Those who had diminished libido had a marked improvement in their symptoms but the effect of TRT on ED was equivocal. In conclusion, this is the first report to show vasculogenic insufficiency in patients with haematological malignancies treated by BMT. Although hypogonadism can account for diminished libido, arteriogenic insufficiency is likely to be an important factor accounting for ED in these patients, especially those treated by TBI. We recommend a comprehensive assessment including endocrine profile and colour flow Doppler study in formulating the best management plan in recipients of high-dose therapy presenting after transplant with ED.