Estrogen Isn't One Hormone: The Truth About Estradiol, Estrone & Estriol

About this episode

When someone says, "estrogen causes cancer" or "estrogen causes blood clots," what estrogen are they talking about? In this episode, Dr. Brendan McCarthy explains one of the biggest misconceptions in hormone replacement therapy (HRT): estrogen isn't a single hormone—it's a family of hormones. Understanding the differences between estradiol, estrone, and estriol can completely change how you view your treatment, your lab work, and the conversations you have with your healthcare provider. You'll learn why the type of estrogen, how it's delivered (oral, patch, injection, pellet), and how it's monitored all matter. Dr. McCarthy also discusses why informed consent goes beyond signing paperwork—it means truly understanding the treatment you're receiving and why it was chosen for you. In this episode: What estradiol, estrone, and estriol actually do Why estrogen is a family—not a single hormone How oral estrogen differs from patches, injections, and pellets Why delivery method changes how your body metabolizes estrogen The difference between bioidentical, synthetic, and animal-derived estrogens Why lab timing and monitoring are essential for safe HRT The importance of true informed consent in hormone therapy Four questions every patient should ask before starting estrogen