FACTORS INFLUENCING ACTIVITIES OF THE TESTIS 41 



A summary of the actions of the pituitary gonadotrophic hormones upon 

 testicular tissue may be stated as follows: 



(1) Pure FSH in small doses stimulates the seminiferous tubules and 

 spermatogenesis with little or no effect upon the interstitial tissue or 

 the accessory reproductive structures, such as the seminal vesicles or 

 prostate gland; 



(2) Small doses of pure LH also stimulate spermatogenesis with little 

 or no stimulation of the accessory structures; 



(3) Pure LH (ICSH) in larger doses stimulates the development of the 

 interstitial tissue with the subsequent secretion of the male sex hor- 

 mone and hypertrophy of the accessory reproductive organs; 



(4) The male sex hormone in some way aids or stimulates the process 

 of spermatogenesis, suggesting that the action of LH occurs through 

 the medium of the sex hormone (fig. 22). 



(Consult Evans and Simpson in Pincus and Thimann, '50, for data and 

 references; also Turner, C. D., '48.) 



The foregoing results of the action of the FSH and LH upon testicular 

 function might suggest that the LH substance alone is essential in the male 

 animal. However, it should be observed that without the presence of FSH, 

 LH is not able to maintain the tubules in a strictly normal manner, the 

 tubules showing a diminution of size. Also, in extreme atrophic conditions 

 of the tubules, pure FSH stimulates spermatogenesis better than similar quan- 

 tities of LH. It is probable that FSH and LH (ICSH) work together to effect 

 complete normality in the male. This combined effect is known as a syner- 

 gistic effect. It also is of interest that the injection of small doses of testosterone 

 propionate into the normal male, with the pituitary gland intact, results in 

 inhibition of the seminiferous tubules, probably due to the suppression of 

 pituitary secretion by the increased amount of the male sex hormone in the 

 blood. However, high doses, while they likewise inhibit the pituitary, result 

 in a level of androgen which stimulates the seminiferous tubules directly 

 (Ludwig, '50). 



Aside from the above actions upon testicular tissue by the luteinizing hor- 

 mone (LH;ICSH) certain other functions of this substance should be men- 

 tioned (see fig. 22). One of these is the apparent dependence of the SertoU 

 cells upon the presence of the interstitial cells (Williams, '50). Interstitial 

 tissue behavior and development in turn relies mainly upon LH (ICSH) 

 (Fevold, '39; Evans and Simpson in Pincus and Thimann, '50). As the sperm 

 are intimately associated with the Sertoli elements during the latter phases 

 of spermatogenesis in which they transform from the spermatid into the form 

 of the adult sperm, a very close association and reliance upon the presence 

 of the luteinizing hormone thus appears to be established in sperm development. 



A further study of the LH factor is associated with the maintenance of 



