Male fertility regulation: the challenges for the year 2000

Abstract

The search for new, safe, effective and reversible contraceptive methods for men is being pursued by several agencies. The most likely developments before the year 2000 would appear to be: the introduction of more easily reversed procedures of vas occlusion; hormonal means of sperm suppression based on infrequent injections of androgens either alone or combined with other gonadotrophin-suppressing agents. Methods based on new drugs or vaccines are unlikely to be developed by the end of the decade. Research is needed to understand the basis of the differences in efficacy of contraceptive steroids in men of different ethnic origin. Equally there is a need to monitor the safety and acceptability of hormonal methods for men. New targets for drug intervention should be pursued through support of basic science, taking advantage of modern cellular and molecular biological techniques. Finally, the subject of Andrology needs to be strengthened throughout the world so that scientists in developing countries can participate fully in this work.

PIP: The search for new, safe, effective, and reversible contraceptive methods for men as pursued by several agencies and probable future developments until the year 2000 is reviewed. A WHO consultation between vasectomy and the risk of cancer of the prostate or testis is unlikely and changes in family planning policies are unwarranted. Research in China has led to the ligation of the vas by percutaneous injection of sclerosing agents through a puncture opening. The suppression of secretion of either both luteinizing hormone and follicle-stimulating hormone (FSH) or of FSH alone; the recovery of circulating androgen to physiological levels; and the assessment of the functional capacity of residual sperm. Hormonal methods comprise the contraceptive efficacy of testosterone enanthate-induced azoospermia and oligozoospermia; and gonadotropin-releasing hormone analogue-androgen combinations. A large number of non-hormonal chemical agents lead to total spermatogenic arrest and to irreversible sterility. Gossypol was studied as an antifertility agent in clinical studies on more than 8000 Chinese men, but its use for contraception was halted owing to the high incidence of irreversibility and serious side effects such as hypokalemia. Among drugs and plant products for inhibition of sperm maturation, Chinese investigation showed that a multiglycoside extract of the plant Tripterygium wilfordii caused reductions in sperm motility and concentration in patients. A program established between Chinese, Thai, and UK centers aims to isolate pure compounds extracted from the plant for antifertility actions. In regard to contraceptive vaccines, passive or active immunization against FSH has resulted in significant decreases in sperm counts in macaque monkeys with inconsistent effects on fertility.