HORMONES IN DIFFERENTIATION OF SEX 



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Fig. 2.29. The effects of testosterone propionate on the development of the urinogenital 

 sinus and prostatic glands in young opossums. A. Extreme hypertrophy of the sinus and 

 prostate in a male aged 50 days, treated from birth ; compare with the condition in a normal 

 male of the same age (C). The effect of the same dose of hormone in a littermate female is 

 shown in B. Female opossums normally never develop prostatic rudiments, as shown in D 

 and E, representing cross-sections through the urinogenital sinus somewhat below (D) and 

 at the point of junction {E) of the lateral vaginal canals (c/. Fig. 2.225). Note the great 

 difference in the volume of prostatic tissue in the treated male (A) as compared with the 

 treated female (B), although dosage and other conditions were the same. 



merely to exaggerate the normal processes 

 of development. With large doses there is a 

 moderate hyperplasia of the sinus epithe- 

 lium in males and a tremendous hyper- 

 trophy of the prostatic glands. But in fe- 

 males a striking deA'elopment of prostatic 

 glands also occurs (although normally the 

 female possesses no prostatic rudiments) to- 

 gether with a change in form, resulting in a 

 sinus that is typically male. Quantitatively, 

 these effects are proportional to dosage, but 

 with the same dosage an interesting sex dif- 

 ference is constantly observed with respect 

 to the magnitude of the response. The pros- 

 tate (Fig. 2.29.4, B) is invariably more 

 strongly developed in male subjects than 

 in females. This difference in size apparently 

 depends on an inherent difference in growth 

 capacity in homologous tissues of different 

 sex genotype when exposed to the same 

 intensity of stimulation (Burns, 1942b, 

 1956a). This effect appears regularly in the 

 case of many other sex structures of the 



opossum as will be seen. The induction of 

 prostatic glands and a male form of sinus 

 is of regular occurrence in female mam- 

 malian embrvos exposed to male hormones 

 (Table 2.3).' 



Two special points concerning prostatic 

 differentiation in young opossums are of in- 

 terest. Brief treatment of female embryos 

 with androgen, just at the time when the 

 prostatic buds are appearing in males, is 

 sufficient to induce buds which are then 

 capable of continued differentiation after 

 the hormone is withdrawn (Moore, 1945 ». 

 This is an unusually clear case of permanent 

 conditioning of a sex structure by brief ex- 

 posure to a hormone at a critical stage in 

 development. Also of interest is the fact that 

 by gradually reducing the dosage of male 

 hormone a level is reached, at approximately 

 5 /xg. per day, which induces prostatic 

 buds in young females which are identical 

 in size and appearance with those of normal 

 males of the same age (Burns, 1942a) . With- 



