[The thymopause: an immunological climacteric]

The part played by the thymus and its products in conferring and maintaining immunological competence is examined. Attention is also devoted to the effect of thymic involution on the immune system, with particular reference to a fall in circulating thymic hormone. Generally speaking, this fall occurs in the 5th decade of life, which can be described as the thymopause. It is accompanied by increased sensitivity to infection and neoplasia. Two lines of intervention are suggested: the use of highly purified, selective hormone fractions after careful evaluation of the functional aspects of the immune system; employment of organ extracts containing all or nearly all the thymic hormones and peptides in an integrated form. It is felt that the second approach is more practicable today, since it permits broad-spectrum interventions through the stimulation of many mechanisms with different sequential steps, and a well-programmed biological rhythm over the course of time.