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Human Contraceptive Pills Causing Sex Changes in Male Frogs

When it first appeared in the 1960s, the birth control method that prevented pregnancies by combining estrogen and progestogen was popularly known as “the Pill.” If male amphibians could talk, they might have a different four-letter word to describe it when they hear the results of a new study that links male amphibian feminization and actual sex changes to exposure to estrogen from “the Pill” in the waters where they live and breed.

European green toad

European green toad

The populations of amphibians around the world are rapidly declining and scientists are scrambling to find reasons. The feminization of males has reduced populations because the males no longer want to mate with females. Matthias Stöck, an amphibian researcher at the IGB research institute in Berlin, suspected an external cause.

According to his study in Scientific Reports, Stöck suspected estrogen ethinylestradiol (EE2), a manmade estrogen with no equivalent in nature that is used in many female contraceptive pills, enters the water supply via urine and cannot be fully removed by sewage treatment. He selected three amphibian species that live in EE2-loaded waters and have shown signs of sex changes: the African clawed frog (Xenopus laevis), tadpoles of the European tree frog (Hyla arborea), and the European green toad (Bufo viridis).

European tree frog

European tree frog

Stöck and his team logged the sex of each amphibian, then exposed them to EE2. They watched for signs of feminization and changes in sex organs and compared them to a control group with no exposure to EE2.

(Insert frog swear words here) The results were depressing. The researchers found a sex reversal occurred from 15 to 100 percent of the time in the amphibians exposed to EE2. Stöck summed up the situation for the frogs and toads:

In addition to other threats, the feminization of populations may contribute to the extinction of amphibian species. Only, if we will be able to actually access these risks, we will be able to eliminate them in the long term.

Can the news get worse? Sure. The sensitivity to EE2 and similar manmade hormones is not the same in all amphibians and cannot be easily extrapolated to other species not tested in the study.

African clawed frog

African clawed frog

One more thing. If the estrogen in the water is affecting amphibians, it’s probably affecting humans as well in similar ways. Can we improve water treatment to remove all estrogen in the future? Possibly. Can we reduce the amount of estrogen used in contraceptive and the used of estrogen-based contraceptives in general? Good luck with that.

Are the amphibians in trouble because of us? Yep. Are we?

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Paul Seaburn is the editor at Mysterious Universe and its most prolific writer. He’s written for TV shows such as "The Tonight Show", "Politically Incorrect" and an award-winning children’s program. He's been published in “The New York Times" and "Huffington Post” and has co-authored numerous collections of trivia, puzzles and humor. His “What in the World!” podcast is a fun look at the latest weird and paranormal news, strange sports stories and odd trivia. Paul likes to add a bit of humor to each MU post he crafts. After all, the mysterious doesn't always have to be serious.
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