In today’s episode, I’m opening the first chapter of what I believe is the most important series I’ve ever created — a deep dive into progesterone and why it became the heart of my medical practice.

For more than 20 years, I’ve watched this “simple, humble hormone” transform women’s lives in ways most conventional medicine overlooks. What started in two small treatment rooms has grown into a 25,000 sq ft facility, and the core of our success comes down to understanding progesterone’s impact on the female brain, stress response, and emotional resilience.

In this episode, I break down:

Why progesterone is far more than a reproductive hormone

How it regulates the female stress response (amygdala, hippocampus, prefrontal cortex)

Why anxiety, insomnia, irritability, and emotional overwhelm often map directly to progesterone decline

Why so many women feel “unraveled” in their 40s — and why it’s not their fault

The science behind oral vs. sublingual progesterone (and why I use troches)

How conventional medicine often misses the root cause

The importance of physicians showing their work, their data, and their citations

The lived stories and clinical outcomes that changed how I practice medicine

If you’ve ever felt dismissed, unseen, or told that your anxiety or mood changes are “just stress,” this episode is for you.

This is the beginning of a 7-part series where I break down the neurobiology, endocrinology, testing, dosing, delivery methods, breast health, perimenopause, and more.

Citations: Brinton, Roberta Diaz, et al. “Neurosteroids and Brain Function.” Steroids, vol. 81, 2014, pp. 61–78. Epperson, C. Neill, et al. “New Insights into Perimenopausal Depression: A Neuroendocrine Vulnerability Framework.” The Lancet Psychiatry, vol. 9, no. 2, 2022, pp. 110–118. Frye, Cheryl A. “Neurosteroids—Endogenous Modulators of GABA_A Receptors.” Pharmacology & Therapeutics, vol. 116, no. 1, 2007, pp. 58–76. Genazzani, Andrea R., et al. “Progesterone, Stress, and the Brain.” Human Reproduction Update, vol. 16, no. 6, 2010, pp. 641–655. Meeker, John D., et al. “Environmental Endocrine Disruptors: Their Effects on Human Reproduction and Development.” Reproductive Toxicology, vol. 25, 2008, pp. 1–7. Mellon, Stanley H. “Neurosteroid Regulation of Central Nervous System Development.” Pharmacology & Therapeutics, vol. 116, 2007, pp. 107–124. Mizrahi, Romy, et al. “The Role of Allopregnanolone in Stress, Mood, and Trauma.” Neurobiology of Stress, vol. 11, 2019, 100198. Paul, Steven M., and Graziano Pinna. “Allopregnanolone: From Molecular Pathways to Therapeutic Applications.” Current Opinion in Neurobiology, vol. 48, 2018, pp. 90–96. Pluchino, Nicoletta, et al. “Progesterone and Allopregnanolone: Effects on the Central Nervous System in the Luteal Phase and in Perimenopause.” Gynecological Endocrinology, vol. 36, no. 6, 2020, pp. 441–445. Rasgon, Natalie L., et al. “Perimenopausal Changes in the Brain and Mood: A Review.” Journal of Clinical Endocrinology and Metabolism, vol. 107, no. 4, 2022, pp. 1120–1134. Reddy, Doodipala Samba. “The Neurosteroid Allopregnanolone and GABA-A Receptor Modulation in Epilepsy and Mood Disorders.” Frontiers in Neuroscience, vol. 12, 2018, 933. Schiller, Crystal E., et al. “The Neuroendocrinology of Perimenopausal Depression.” Trends in Neurosciences, vol. 44, no. 2, 2021, pp. 119–135. Schumacher, Michael, et al. “Neuroprotective Effects of Progesterone and Its Metabolites.” Frontiers in Neuroendocrinology, vol. 33, 2012, pp. 415–439. Selye, Hans. “The General Adaptation Syndrome and the Diseases of Adaptation.” Journal of Clinical Endocrinology, vol. 6, no. 2, 1946, pp. 117–230. Sheng, Jun, and György Buzsáki. “Neuronal Firing and Theta Oscillations in the Amygdala During Fear Conditioning.” Neuron, vol. 53, 2007, pp. 653–667. Smith, Sheryl S. “Progesterone Withdrawal Increases Neuronal Excitability in the Hippocampus: A GABA_A Mechanism.” Journal of Neuroscience, vol. 28, 2008, pp. 10171–10179. Snyder, Jonathan S., et al. “Adult Hippocampal Neurogenesis and Stress Regulation.” Nature Reviews Neuroscience, vol. 12, 2011, pp. 1–9. Stanczyk, Frank Z., and Jerilynn C. Prior. “Progesterone and Progestins: A Review of Pharmacology, PK, and Clinical Use.” Steroids, vol. 82, 2014, pp. 1–8. Tu, Ming-Je, et al. “Oral, Vaginal, and Transdermal Progesterone: PK, Metabolism, and Tissue Distribution.” Drug Metabolism Reviews, vol. 52, no. 2, 2020, pp. 1–28. Wang, Jun, et al. “Stress, Amygdala Plasticity, and the Neuroendocrine Interface.” Nature Neuroscience, vol. 10, 2007, pp. 1093–1100. Weinstock, Marta. “The Hippocampus and Chronic Stress.” Neurochemical Research, vol. 42, 2017, pp. 1–12. World Health Organization. Progesterone and Reproductive Function: Clinical Perspectives. WHO, 2019.

Dr. Brendan McCarthy is the founder and Chief Medical Officer of Protea Medical Center in Arizona. With over two decades of experience, he’s helped thousands of patients navigate hormonal imbalances using bioidentical HRT, nutrition, and root-cause medicine. He’s also taught and mentored other physicians on integrative approaches to hormone therapy, weight loss, fertility, and more. If you’re ready to take your health seriously, this podcast is a great place to start.

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Website: www.protealife.com

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