Hormones & The Environment: What We Can Learn from Frogs

If you wanted to know everything about sex but you were ahead of your time--say a teenager in the 1930s--you may have done what a bunch of students at Johns Hopkins medical school did.

Their sources were limited. This was 20 years before both Playboy magazine hit the newsstands and Alfred Kinsey's sex surveys (Sexual Behavior in the Human Male and then Sexual Behavior in the Human Female) topped bestseller lists. It was nearly 40 years before The Joy of Sex, Dr. Alex Comfort's illustrated sex manual.

So this curious group of students got their hands on the newly released Sex and Internal Secretions, edited by Dr. Edgar Allen, the scientist who discovered estrogen.

Sex and Internal Secretions was a hefty treasure trove of everything anyone back then would want to know about the burgeoning field of sex studies and sex hormones. It took clever word manipulation to drain the juice out of a sex book. Not joy of sex. This was physiology of sex.

Consider this. Frank R. Lillie, a University of Chicago embryology professor, who wrote the first chapter, provided this description of sexual intercourse: Sex "differs from other universal organic functions such as metabolism, or irritability in requiring two individuals for its complete expression," he wrote. It takes clever word manipulation to drain the juice out of a sex book.

The crux of the discussion among the dozen or so students who met to study Sex and Internal Secretions was about the biology of sex differentiation. Which chemicals, if any, trigger the embryo to become female or male? What controls maleness and femaleness and what do those labels mean anyhow? Was it all to do with something inherited? Hormones? Or something else?

I was thinking about those students when I read an article in the recent issue of Yale Medicine. Scientists noticed nearly twice as many female frogs born among 21 backyard ponds than would be expected. They suspect a link between the estrogen-like substances in the flowers planted near the suburban ponds and the uptick in female frogs. The full report was published last fall in the Proceedings of the National Academy of Scientists.

We seem to have come full circle when it comes to hormones. Back when the Hopkins students were meeting at the local diner to read chapters of their sex textbook aloud, they were wondering about how the environment could impact the development of growing fish, frogs and maybe even humans. Some studies in the book pointed to a mother's diet or the heat of her womb and its impact on hormones and how that altered the growing fetus.

All of this was pushed to the backburner with the mid-twentieth century discovery of sex chromosomes (XX equals girls and XY equals boy). The discovery of the so-called "Barr body" (the extra blob on the end of a chromosome that turned a Y looking one into an X one) trumped everything else we thought we knew about the environment and hormones.

But no longer. These days we are starting to realize that our inherited Xs and Ys provide the template. But then outside forces (perhaps chemicals, diet, or even trauma) effect our hormones and how they interact with each other, shaping the way tadpoles become frogs and babies become grown-ups.

The point is not simply to fear the pollutants that may slip into the waters and wreak havoc on developing fetuses--though we should. But really, the history of endocrinology and nearly every new emerging study should challenge us to change the way we think about our hormonal selves. We are, after all, part of a vast and connected ecosystem shifting not just our backyard ponds and the little tadpoles inside them, but our inner human landscape as well.

Why Do Any of Us Right: Read Suzanne Koven, MD's piece on medical memoirs (it may help the reader, but it's healing for the writer).