The metabolism of testosterone.

The functional significance of the testis has been known since the time of Aristotle (121) who ascribed post-pubertal changes to the function of the gonads, as such manifestations were absent in castrates — both in man and in birds. Accurate knowledge of the nature and metabolism of the androgenically active substance secreted by the testis has, however, been acquired only during the past decade. It was not until the first half of the Nineteenth Century that the gonads were recognized as being ductless glands, and capable of secreting a substance into the blood-stream. That the testis is normally the main source of the androgenic substance in man and other animals was first indicated experimentally by Berthold in 1849 (4). He removed the testis of four roosters and replaced one testis in an unusual abdominal position in each of two capons. He killed these two capons six months later and found that because of the testicular grafts, “these animals remained male in regard to voice, reproduction, instinct, fighting spirits, and growth of comb and wattles”. Berthold further suggested that the testicle exerted its influence upon the organism via the blood, and this viewpoint is now the generally accepted one. [...