Male fertility regulation: recent advances*

A four-centre study conducted by the National Institutes of Health in the USA addressed the two major concerns for the use of the most long-acting ester available, testosterone enanthate, i.e., the frequency with which intramuscular injections must be given and the possible side-effects. [...] A 5-country acceptability study conducted by the WHO human reproduction programme in 1976 showed that while the monthly administration of an antifertility agent to men by injection was not unacceptable, most of the men stated that they preferred a pill to the injection as a route of administration. [...] New work on the cloning and sequence analysis of cDNA coding for the a- and j6-chains of porcine inhibin (20) and bovine inhibin (21) takes the possibility of the genetic engineering of inhibin a major step forward. [...] While the results are encouraging, a combination of two steroids with such radically different pharmacokinetic reactions is likely to lead to the lack of uniformity in the responses that have been observed and also to raise serious concerns about the effects on liver function from long-term use with the administration of 600-800 mg doses of steroid per day. [...] It is evident that one of the major advances in the field would be the development of a much longer-acting androgen hormone yielding a continuous slow release of testosterone over a period of several months.