In 1982, Jane Fonda put out her first exercise video. That VHS tape helped spark an exercise craze. But the exercise craze also made a lot of people suddenly lose their periods. Doctors were confused. Was this a temporary reaction due to all the exercise? Was this forever? Were these women still fertile? Our guest today, Virginia Vitzthum, decided to dig in and research these exact questions. Dr. Vitzthum is the head of scientific research at Clue, and a senior scientist at the Kinsey Institute. For more information on today's episode visit helloclue.com/hormonal. And to find out how to support the work here at Clue, go to Clue.Plus. Want to know the answer to the question at the beginning of the show? Check out Can you get pregnant from "precum"? on helloclue.com. Background Reading: Helloclue.com: What is an "irregular" menstrual cycle? Helloclue.com: Hormones and your environment: a conversation with Dr. Virginia J. Vitzthum Helloclue.com: Hormones and culture: How reproductive hormones vary across cultures