Steinach and Young, discoverers of the effects of estrogen on male sexual behavior and the “male brain”

Abstract

In the 1930s Eugen Steinach´s group found that estradiol induces lordosis in castrated rats and reduces the threshold dose of testosterone necessary for induction of ejaculation, and that estradiol-treated intact rats display lordosis as well as mounting and ejaculation. The bisexual, estrogen-sensitive male had been demonstrated. Another major, albeit contrasting, discovery was made in the 1950s, when William Younǵs group reported that male guinea pigs and prenatally testosterone-treated female guinea pigs are relatively insensitive to estrogen when tested for lordosis as adults. Reduced estrogen-sensitivity was part of the new concept of organization of the neural tissues mediating sexual behavior of females, into tissues similar to those of males. The importance of neural organization by early androgen stimulation was realized immediately and led to the discovery of a variety of sex difference in the brain of adult animals. By contrast, the importance of metabolism of testosterone into estrogen in the male was recognized only after a delay. While the finding that males are sensitive to estrogen was based on Bernhard Zondek´s discovery in 1934 that testosterone is metabolized to estrogen in males, the finding that males are insensitive to estrogen was based on the hypothesis that testosterone - male sexual behavior is the typical relationship in the male. It is suggested that this difference in theoretical framework explains the discrepancies in some of the reported results.

Significance Statement: In 1936, the importance of estrogen in male sexual behavior was discovered. This finding went unnoticed when estrogeńs effect in the male was re-discovered in the early 1970s; the original report of the effect of estrogen in the male in 1936 was found only in 2012. An equally significant discovery was made in 1959, when it was found that prenatal treatment with testosterone organizes the brain of a female into a male brain and permanently decreases behavioral estrogen sensitivity. Males cannot be both sensitive and insensitive to estrogens and this inconsistency may have contributed to the long latency before the significance of estrogen in the male was recognized.