Testicular testosterone biosynthesis in male Saanen goats with XX sex chromosomes

Testosterone biosynthesis was examined in three pairs of twin male Saanen goats. In each pair, one goat was a phenotypically normal male of XY chromosome constitution; the other showed testicular hypoplasia of the sort typically associated with homozygosity for the dominant gene for polledness in genetic females, and was of XX chromosome constitution. The histological and hormonal situations in the hypoplastic male goats resembled those found in Kleinfelter and XX human males, both in their nature and in their variability. Histological examination of the testes of the hypoplastic XX males showed various degrees of degeneration. In one case a “sperm pocket” full of spermatozoa was observed, and in this case sperm cells with heads separated from tails were observed in the semen. In the other two cases semen was devoid of sperm cells. In two cases plasma testosterone levels of the hypoplastic goats were lower than those of their normal counterparts, in one of the cases much lower. When testicular microsomal fractions of these goats were tested for their in vitro ability to bring about the conversion of androstenedione to testosterone, it was observed that 17β‐hydroxysteroid dehydrogenase activity was either absent or lower in the hypoplastic goats than in their normal twins. In the third pair of animals, plasma testosterone levels were similar in both normal and hypoplastic animals. In this case, however, the increase in testosterone levels following HCG administration was lower in the hypoplastic than in the normal goats. 3β‐hydroxysteroid dehydrogenase was the same in normal and hypoplastic goats. The variable effects on testosterone biosynthesis support the notion that the sex chromosomes, while affecting steroid biosynthesis in the testis, do so indirectly.