Steroid biosynthesis and the brain-testis axis

The significanee of testicular tunetion was shown as l early as 1849 by Berthold when he observed atrophy of the comb in castrated cockerels, which could be restored by implantation of a testis in the abdomen. It was only in the beginning of the twentieth century, however, that Bouin and Ancel postulated the formation of certain horrnonal principles in distinct cell types of the testis. The identification of testasterene as the biologically active andregen of the bull testis in 1935 rnarked the beginning of biochemical studies of testis function. The measurement of testicular horrnonal products has been difficult for a long time because only small quantities are produced. However, present techniques such as radioimmunoassay permit the measurement of picogram quantities of testosterone4. Parallel with the development of these techniques, insight has been gained into the endocrine function of the testis.