334 



PHYSIOLOGY OF GOKADS 



Fig. 5.17. Stages of sexual development and maturation. (From W. A. Schonfeld, Ai 

 J. Dis. Child., 65, 535, 1943.) 



(HCG) increases the yield of testosterone 

 from testicular slices incubated with ace- 

 tate. Estradiol- 17-/? also has been found 

 in the products obtained by incubating tis- 

 sue slices with acetate. Human testicular 

 tumors incubated with labeled acetate form 

 labeled testosterone, androstenedione, pro- 

 gesterone, estradiol, and estrone (Wotiz, 

 Davis and Lemon, 1955). Mevalonic acid, a 

 precursor of cholesterol, yields estradiol 

 when incubated with homogenates of hu- 

 man testis (Rabinowitz and Ragland, 

 1958). The biogenesis of male hormone as 

 worked out in the stallion, rat, and human 

 (Savard, Dorfman and Poutasse, 1952; Sav- 

 ard, Besch, Restivo and Goldzieher, 1958; 

 Savard, Dorfman, Baggett and Engel, 1956) 

 by means of radioisotopic methods shows a 

 common pathway from 17a-hydroxyprogcs- 

 terone -^ progesterone -> 4-androstene- 

 3,17-dione —^ testosterone. Testosterone has 

 been identified in the spermatic vein blood 

 of dogs (West, Hollander, Kritchevsky and 

 Dobriner, 1952). Also identified were A^- 

 androstcno(lione-3-17 and 7-keto-cholester- 

 one. 



In addition to confirming the presence of 



several biologically active steroids in the 

 testis, the studies made in the last two 

 decades have clarified the biosynthesis of 

 male hormone. The peripheral metabolism 

 of testosterone and its biologic actions in 

 the organism are described in chapters by 

 Villee and by Price and Williams-Ashman, 

 respectively. 



In addition to these well-known steroid 

 hormones, the presence of a water-soluble 

 hormone in the testis has been postulated on 

 biologic evidence. Vidgoff, Hill, Vehrs and 

 Kubin (1939) and Vidgoff and Vehrs (1941) 

 induced atrophy of the testis and accessory 

 sex organs in the rat by the administration 

 of aqueous extracts of bull testes. Because 

 the atrophy was similar to that occurring 

 after hypophysectomy, it was claimed that 

 a water-soluble principle in the testis was 

 capable of inhibiting the gonadotrophic 

 function of the ])ituitary. This principle was 

 called "inhibin." The theory was then con- 

 structed that the testis secretes two hor- 

 mones, nnnu'ly a water-soluble hormone 

 responsible for the integrity of the germi- 

 nal epithelium by regulating the secretion 

 of pituitary gonadotrophin, and a fat- 



