Current status of studies concerned with evaluation of toxic effects of chemicals on the testes.

A brief review of the history of the subject is provided. An attempt is made to define the current status of the knowledge and the reasons why our knowledge in this area of science is poor. The information gained from studies employing lower species is contrasted with information on the human male. The most commonly utilized techniques for evaluating the effects of toxic agents on the male reproductive system is briefly summarized. The growth of knowledge in physiology, biochemistry, and hormonal control of testicular function during the past ten to fifteen years is discussed; and, the specific most pertinant advances are noted. The difficulties in utilizing the human subject for toxicologic studies are pointed out and the reasons why the knowledge of the effect of toxic agents on the human testes are meager are discussed. The methodology utilized for the study of the functional integrity of the human testes and the specific parameters widely utilized for this purpose are discussed and criticized. The fact that it is extremely difficult to evaluate changes in the testicular function of men are emphasized and the extremely wide variability is pointed out. Furthermore, it is demonstrated that at this moment, we are lacking some of the most fundamental information concerning the normal function of the human testes; and, that there is a poor understanding of parameters of "normalcy". The three parameters used most commonly to define normalcy of human testes, namely, testicular histology, sperm output, and hormonal levels are discussed and the difficulties and pitfalls of these measurements are pointed out.