Progress in research into new methods of fertility regulation for men.
Research results by the UNDP/UNFPA/WHO/World Bank Special Program in Human Reproduction published in 1990 showed that hormones can be used to reduce men's sperm levels to virtual infertility. Weekly injections of testosterone enanthate (TE) produced azoospermia in most men. A multicenter study was also completed in 1994 involving a total 399 men in nine countries who were given regular injections of TE. High contraceptive effectiveness resulted among those men whose sperm concentrations were reduced to 3 million or less per ml (oligozoospermia). The failure rate was 1.4 pregnancies per 100 person-years, similar to that of oral contraceptives. It took an average of 68 days to reach oligozoospermic and 100 days to reach azoospermic sperm counts after the 1st injection. To return to normal levels after the last injection took 112 days and 203 days, respectively, in oligozoospermic and azoospermic men. Testing of testosterone buciclate (TB) was also carried out in Germany to assess the effect of longer-acting androgen esters suppressing gonadotrophin secretion. Azoospermia was achieved in some men by giving a single dose of 1200 mg of TB, but at half that dose oligozoospermia was not reached. Research is also continuing into the male contraceptive effect of progestogen-androgen combinations. Progestogen prevents the production of sperm at much lower doses than androgen. Androgen is given to replace testosterone that is inhibited as a result of the suppression of gonadotrophin, but it is needed less frequently. The combination seems to suppress sperm production more quickly than the androgen alone. In China, India, and Indonesia, plans are prepared for efficacy studies with such combinations. The drawback for large-scale use is that the components have to be injected at different intervals. This may be overcome by combining TB with a progestogen with the same duration of action and giving both at the same time.