Conversion of androgens to estrogens in the male squirrel monkey (Saimiri sciureas)

Many New World primates such as the squirrel monkey have extraordinarily high plasma levels of steroid hormones including cortisol, testosterone, progesterone and vitamin D3. While plasma estrogen levels in female squirrel monkeys apparently are approximately the same as those found in other species no information is available for males. The present results indicate that the plasma levels of estrone (E1), estradiol (E2), and E1 sulfate are approximately 10-fold higher than those found in men. Comparative in vitro studies of androgen metabolism in genital skin fibroblasts indicate that squirrel monkey cells have higher aromatase and lower 5-alpha-reductase activity than human cells. Estimation of aromatase activity in vivo by a radiometric assay indicates that the high plasma estrogens are derived by peripheral conversion from testicular and/or adrenal androgens.