Dr. Brendan McCarthy

Dr. Brendan McCarthy
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Welcome! Dr. Brendan McCarthy founded Protea Medical Center in 2002. While he’s been the chief medical officer, Protea has grown and evolved into a dynamic medical center serving the Valley and Central Arizona. Through successful case after successful case, Dr. McCarthy has been dedicated to hormone balance, healthy metabolism, and the best quality of life. Dr. McCarthy’s hallmark is his unorthodox approach to mental/emotional wellness and its link to hormone balance in women and men. Through the use of blood work and clinical investigation, Dr. McCarthy gets to the bottom of possible causes for common conditions such as anxiety, PMS, depression, slow metabolism, weight gain, insomnia and now wants to share his knowledge to the viewers with his podcast. Join the discussion, ask questions, and welcome to the podcast!

  1. 6D AGO

    The Real Reason You Crave Junk Food Under Stress

    Is weight gain really about willpower… or is something deeper going on? In this episode, Dr. Brendan McCarthy, Chief Medical Officer at Protea Medical Center, breaks down the real biology behind stress, cravings, and weight gain—and why blaming yourself (or cortisol) is missing the point. You’ll learn: Why chronic stress rewires your metabolism How stress drives cravings for ultra-processed foods The truth about cortisol and fat storage Why “just have more discipline” is bad medicine How ultra-processed foods hijack your hunger and reward systems The key to rebuilding control and agency This isn’t about motivation—it’s about understanding your biology so you can finally work with your body instead of against it. If you’ve ever felt stuck, frustrated, or blamed for your weight… this episode is for you.   Mechanism-Anchored References     1.    Glucocorticoids, stress, and eating Kuckuck S, van der Valk ES, Scheurink AJW, et al. Glucocorticoids, stress and eating: the mediating role of appetite-regulating hormones. Obesity Reviews. 2023. Supports the claim that stress biology and glucocorticoid signaling can alter appetite regulation and eating behavior.       2.    Stress-level glucocorticoids can increase hunger Bini J, et al. Stress-level glucocorticoids increase fasting hunger and alter cerebral blood flow in neural regions that regulate food intake. 2022. Supports the claim that stress-level glucocorticoid exposure can increase hunger and affect food-intake regulation.       3.    Stress-obesity link / HPA-axis context Lengton R, et al. Glucocorticoids and HPA axis regulation in the stress-obesity link. 2024. Supports the broader claim that chronic stress and glucocorticoid biology are relevant to obesity risk and metabolic dysregulation.       4.    Sleep loss changes appetite and metabolism Van Cauter E, et al. Metabolic consequences of sleep and sleep loss. 2008. Supports the claim that inadequate sleep alters appetite regulation and harms carbohydrate metabolism.       5.    Sleep deprivation impairs glucose handling and raises appetite pressure Knutson KL. The metabolic consequences of sleep deprivation. 2007. Supports the claim that sleep loss can worsen glucose metabolism, appetite drive, and obesity risk.       6.    Circadian disruption and metabolic dysfunction Depner CM, et al. Metabolic consequences of sleep and circadian disorders. 2014. Supports the claim that circadian disruption and sleep deficiency contribute to metabolic dysregulation and weight gain risk.       7.    Ultra-processed food and reward-system activation Calcaterra V, et al. Ultra-Processed Food, Reward System and Childhood Obesity. 2023. Supports the claim that ultra-processed foods interact with reward pathways in ways that can drive intake beyond simple calorie math.       8.    Ultra-processed food and metabolic dysfunction Vitale M, et al. Ultra-Processed Foods and Human Health: A Systematic Review and Meta-Analysis. 2023. Supports the claim that higher UPF consumption is associated with obesity and metabolic disease risk.       9.    Stress and poorer diet quality / emotional eating Shatwan IM, et al. Association between perceived stress, emotional eating, and diet quality. 2024. Supports the claim that higher perceived stress is associated with worse dietary patterns and emotional eating.       10.    Compassion-based framing and adherence Sirois FM, et al. Self-Compassion and Adherence in Five Medical Samples. 2018. Supports the closing point that shame is a weak intervention model and that compassion-linked framing may better support adherence and change.     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.   👇 Tap Subscribe to learn more about what’s actually happening in your body, and what to do about it.   📘 Read Dr. McCarthy’s Book: Jump Off the Mood Swing – A Sane Woman’s Guide to Her Crazy Hormones https://www.amazon.com/Jump-Off-Mood-Swing-Hormones/dp/0999649604   📲 Follow Dr. McCarthy: Instagram: @drbrendanmccarthy TikTok: @drbrendanmccarthy Website: www.protealife.com   💬 Got a question or topic for a future episode? Let us know in the comments!

    18 min

  2. MAR 19

    The Missing Piece in Weight Loss

    We’ve all heard it: calories in vs. calories out. And while that’s not wrong… it’s not complete. Dr. McCarthy breaks down the three major approaches to weight loss: 1. Calorie restriction 2. Insulin management (low-carb, keto, etc.) 3. Exercise & performance …and explains why each works—but still falls short on its own. The missing piece? The signal your food sends to your body. This episode explores how ultra-processed foods: - Disrupt hunger and satiety signals - Spike blood sugar and drive cravings - Bypass normal metabolic pathways - Create instability in an otherwise well-designed system Citations: Protea Mechanism-Anchored Evidence Map Episode 4 — Insulin Is Not the Enemy: Misrouted Energy Is Below are key scientific principles and supporting literature behind this episode. This is not about “proving a point”—it’s about giving you a transparent look at how these conclusions are built. 1. Energy Balance Is Real—But Regulated Body weight isn’t controlled by calories alone. Hormones, the brain, appetite, and behavior all regulate how energy is used, stored, and burned. Key refs: Hall et al. (2012); Speakman & Westerterp (2010) 2. Insulin Is a Traffic Director, Not the Villain Insulin helps route nutrients (to muscle, liver, or fat). It doesn’t independently cause obesity—it directs where energy goes. Key refs: Saltiel & Kahn (2001); Petersen & Shulman (2018) 3. No Single Model Explains Everything Calories matter. Hormones matter. Behavior matters. A complete model integrates all three—not just one. Key refs: Ludwig et al. (2022); Hall & Chow (2015) 4. Exercise Helps—But Isn’t the Full Solution Exercise improves metabolism and health, but often doesn’t override poor dietary signaling due to compensation (hunger, adaptation). Key refs: Swift et al. (2014); Pontzer et al. (2016) 5. Food Is More Than Calories—It’s Information Food sends signals that impact hunger, metabolism, hormones, and brain reward systems—not just energy intake. Key refs: Morton et al. (2006); Friedman (2004) 6. Ultra-Processed Foods Disrupt Regulation These foods increase intake by altering satiety, speed of eating, and reward pathways—leading to overeating. Key refs: Hall et al. (2019); Monteiro et al. (2019) 7. Fructose Is Metabolized Differently Fructose is processed primarily in the liver and more readily contributes to fat production (de novo lipogenesis). Key refs: Tappy & Lê (2010); Softic et al. (2020) 8. Muscle & Protein Drive Metabolic Stability Protein supports satiety and thermogenesis, while muscle helps regulate glucose and overall metabolic health. Key refs: Leidy et al. (2015); DeFronzo et al. (2009)   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.   👇 Tap Subscribe to learn more about what’s actually happening in your body, and what to do about it.   📘 Read Dr. McCarthy’s Book: Jump Off the Mood Swing – A Sane Woman’s Guide to Her Crazy Hormones https://www.amazon.com/Jump-Off-Mood-Swing-Hormones/dp/0999649604   📲 Follow Dr. McCarthy: Instagram: @drbrendanmccarthy TikTok: @drbrendanmccarthy Website: www.protealife.com   💬 Got a question or topic for a future episode? Let us know in the comments!

    20 min

  3. MAR 12

    Why You’re Still Hungry After Eating

    Why do you crave dessert after dinner? Why are you hungry again an hour after eating? And why does weight sometimes seem to accelerate even when you're watching calories? In Episode 3 of this series on ultra-processed and hyper-palatable foods, Dr. Brendan McCarthy breaks down the biology behind cravings, hunger, and weight gain. This episode connects the dots between food engineering, blood sugar spikes, insulin, and the brain’s reward system—showing why this isn’t a willpower problem, but a biological response to the foods we’re eating. Dr. McCarthy, Chief Medical Officer at Protea Medical Center in Tempe, Arizona, explains how modern ultra-processed foods are designed to override normal satiety signals, destabilize blood sugar, and drive continued consumption. Over time, this can create hormonal changes that make weight gain easier and weight loss harder. In this episode you’ll learn: • Why ultra-processed foods trigger cravings and repeat eating • How glycemic spikes lead to hunger shortly after meals • The role of insulin as a “routing hormone” for calories • How food processing affects fat storage in the body • Why weight gain can accelerate over time • Why this is not a failure of willpower This series focuses on precision nutrition and endocrinology, helping you understand the real biological mechanisms behind metabolism, hunger, and weight regulation. If you’ve ever wondered why controlling food intake feels so difficult despite your best efforts, this episode will help you understand what your body is actually responding to.   Citations: Episode 3 — Mechanism-Anchored Evidence Summary This episode explores how ultra-processed foods, liver metabolism, adipose tissue, hormones, and brain signaling interact to drive cravings, fat storage, and weight gain. Key mechanisms and supporting references include: Hepatic First-Pass Metabolism: Carbohydrates enter the liver via portal circulation, controlling post-meal fuel distribution (Samuel & Shulman, 2016). Fructose and Lipogenesis: Fructose bypasses key glycolytic regulation, fueling hepatic fat synthesis (Softic et al., 2020). De Novo Lipogenesis: Excess carbs activate SREBP-1c and ChREBP, producing triglycerides in the liver (Donnelly et al., 2005). VLDL Export: Hepatic triglycerides are packaged into VLDL and sent to adipose tissue (Adiels et al., 2008). Adipose Storage: Lipoprotein lipase delivers circulating triglycerides to fat cells (Kersten, 2014). Insulin Resistance: Hepatic lipid accumulation impairs insulin signaling (Samuel et al., 2004). Hyperinsulinemia & Fat Storage: Insulin promotes triglyceride storage and suppresses lipolysis (Czech, 2017). Aromatase & Estrone: Expanded adipose increases aromatase activity, raising estrone levels (Simpson et al., 1999; Key et al., 2002). Inflammation: Enlarged fat cells release cytokines, worsening insulin resistance (Hotamisligil, 2006). Ultra-Processed Foods & Overeating: Highly palatable foods drive excess calorie intake (Hall et al., 2019). Reward Signaling: Dopamine pathways reinforce eating behaviors (Volkow et al., 2013). Satiety Disruption: Low fiber and processed structure bypass satiety hormones like GLP-1 and PYY (Slavin & Green, 2007). Synthesis: Ultra-processed foods → rapid hepatic load → lipogenesis → triglyceride export → adipose expansion → estrone increase → inflammation & insulin resistance → cravings and repeated consumption. This creates a self-reinforcing metabolic cycle linking diet, liver, adipose tissue, hormones, and behavior.   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.   👇 Tap Subscribe to learn more about what’s actually happening in your body, and what to do about it.   📘 Read Dr. McCarthy’s Book: Jump Off the Mood Swing – A Sane Woman’s Guide to Her Crazy Hormones https://www.amazon.com/Jump-Off-Mood-Swing-Hormones/dp/0999649604   📲 Follow Dr. McCarthy: Instagram: @drbrendanmccarthy TikTok: @drbrendanmccarthy Website: www.protealife.com   💬 Got a question or topic for a future episode? Let us know in the comments!

    21 min

  4. MAR 5

    Why You Can’t Stop Craving Ultra-Processed Foods (It’s Not Willpower)

    In this episode, we’re diving deep into ultra-processed foods — and why cravings in your 30s, 40s, and 50s are not a character flaw. If you’ve ever: Felt compulsive around certain foods Wondered why you “used to have more willpower” Eaten for stress relief and felt ashamed afterward Asked yourself why your partner can stop but you can’t This episode is for you. There are three major biologic reasons why cravings intensify during this season of life: 1️⃣ Engineered hyper-palatable foods Modern ultra-processed foods are scientifically designed to manipulate salt, sugar, fat, texture, and glycemic response — overriding normal satiety signals and strengthening dopamine tagging in the brain. 2️⃣ Chronic stress physiology Stress amplifies cravings for energy-dense foods. These foods temporarily shift serotonin and dopamine signaling, creating relief — but worsening the long-term cycle. 3️⃣ Perimenopause & progesterone decline As ovarian reserve shifts in your late 30s and beyond, progesterone drops. Less allopregnanolone support at the GABA receptor means higher anxiety tone — and weaker “brakes” on impulse control. This isn’t about willpower. It was never a fair fight.   Citation: Episode 2 – Mechanism-Anchored Evidence Map: Ultra-Processed Foods, Reward Signaling, Stress, and Hormonal Vulnerability Ultra-Processed Food Engineering – Salt, sugar, fat, and texture are manipulated to maximize reward signaling and overconsumption. (Fazzino et al., 2019; Gearhardt et al., 2011; Hall et al., 2019) Dopamine and Reward Tagging – Dopamine marks important stimuli, reinforcing repeated behavior and “wanting” rather than pleasure. (Schultz, 2016; Berridge & Robinson, 1998) High-Glycemic Carbohydrates – Increase tryptophan availability and serotonin synthesis, influencing mood and short-term relief. (Fernstrom & Wurtman, 1972; Wurtman & Wurtman, 1989) Chronic Stress – Alters reward circuitry, increasing vulnerability to compulsive behaviors. (Piazza & Le Moal, 1998; Sinha, 2008) Progesterone, Allopregnanolone, and GABA – Hormonal neurosteroids modulate GABAergic inhibition, stress buffering, and reward sensitivity. (Paul & Purdy, 1992; Reddy, 2010; Purdy et al., 1990) Sleep and Appetite Regulation – Hormonal and neurosteroid pathways influence sleep; sleep disruption increases hunger and cravings. (Tasali et al., 2004; Purdy et al., 1990) Summary: These mechanisms explain why hyper-stimulating foods are particularly compelling during chronic stress and hormonal transitions, showing cravings are biologically reinforced rather than a matter of willpower.   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.   👇 Tap Subscribe to learn more about what’s actually happening in your body, and what to do about it.   📘 Read Dr. McCarthy’s Book: Jump Off the Mood Swing – A Sane Woman’s Guide to Her Crazy Hormones https://www.amazon.com/Jump-Off-Mood-Swing-Hormones/dp/0999649604   📲 Follow Dr. McCarthy: Instagram: @drbrendanmccarthy TikTok: @drbrendanmccarthy Website: www.protealife.com   💬 Got a question or topic for a future episode? Let us know in the comments!

    16 min

  5. FEB 25

    Ultra-Processed Foods: Why You Can’t Stop Eating Them

    If you're a woman in your late 30s, 40s, or 50s and you feel swollen, inflamed, stuck, exhausted, or like your body has completely turned against you — this series is for you. Let’s be clear: This is NOT a diet episode. This is NOT food shaming. This is NOT about willpower. This is upstream endocrinology. In this episode, Dr. McCarthy explains: Why weight gain in perimenopause is not a discipline problem How estrogen dominance and low progesterone shift insulin sensitivity Why stress hormones (like cortisol) amplify fat storage How ultra-processed, hyper-palatable foods hijack your brain Why traditional diets (keto, low-fat, carnivore) often fail women The real role of insulin as a routing hormone — not just a blood sugar hormone Why GLP-1 medications can help — but shouldn’t become “handcuffs” Most nutrition research was built on male physiology. You are not a small man. And it was never a fair fight.   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.   👇 Tap Subscribe to learn more about what’s actually happening in your body, and what to do about it.   📘 Read Dr. McCarthy’s Book: Jump Off the Mood Swing – A Sane Woman’s Guide to Her Crazy Hormones https://www.amazon.com/Jump-Off-Mood-Swing-Hormones/dp/0999649604   📲 Follow Dr. McCarthy: Instagram: @drbrendanmccarthy TikTok: @drbrendanmccarthy Website: www.protealife.com   💬 Got a question or topic for a future episode? Let us know in the comments!

    17 min

  6. FEB 18

    The Progesterone Promise: Why Context Matters More Than the Hype

    In this final episode of the Progesterone Promise series, Dr. Brendan McCarthy, Chief Medical Officer of Protea Medical Center, breaks down one of the most misunderstood hormones in women’s health: progesterone. Progesterone is not “good” or “bad.” It’s contextual. In today’s world of quick sound bites and social media medicine, hormones are often reduced to oversimplified claims like “progesterone fixes anxiety” or “progesterone causes breast cancer.” The truth? It depends on your body, your stress levels, your liver health, your inflammation, your delivery method, and whether you're using bioidentical progesterone or synthetic progestins.   Citations: 1. Oral Progesterone → First-Pass Metabolism & Allopregnanolone Claim: Oral micronized progesterone undergoes significant hepatic first-pass metabolism, increasing neuroactive metabolites (especially allopregnanolone), which positively modulate GABA-A receptors and produce sedative/anxiolytic effects. Core Evidence: Simon et al., 1993; de Lignières et al., 1995; Freeman et al., 1990 — Oral progesterone produces measurable neuroactive metabolites. Paul & Purdy, 1992; Rupprecht et al., 2001 — Allopregnanolone enhances GABA-A receptor activity. Supports: Sedation variability by route • Neurosteroid generation • GABA-A modulation 2. Sulfation vs 5α-Reduction → Opposing Neurologic Effects Claim: Progesterone metabolites can produce calming (5α-reduced) or excitatory (sulfated) neurologic effects depending on enzyme routing. Core Evidence: Majewska et al., 1990 — Pregnenolone sulfate negatively modulates GABA-A. Wu et al., 1991 — Sulfated neurosteroids enhance NMDA signaling. Schumacher et al., 2007; Reddy, 2010 — Pathway reviews of sulfation vs 5α-reduction. Supports: Reverse responding hypothesis • Divergent neurologic experiences • Enzyme-dependent effects 3. Stress & Enzyme Modulation Claim: Chronic stress alters HPA axis tone and hepatic enzyme expression, influencing steroid metabolism balance. Core Evidence: McEwen, 1998 — Allostatic load model. Charmandari et al., 2005 — Cortisol’s systemic regulatory effects. Zanger & Schwab, 2013; Gibson & Skett, 2001 — Stress alters cytochrome P450 expression. Supports: Stress-biased metabolism • Context-dependent hormone response 4. Breast Tissue Signaling & Context Claim: Progesterone influences mammary differentiation and interacts with estrogen signaling in context-dependent ways. Core Evidence: Brisken & O’Malley, 2010 — Progesterone receptor biology in breast tissue. Beleut et al., 2010 — RANKL mediates progesterone-driven proliferation. Hofseth et al., 1999 — PR-ER signaling interaction. Stanczyk & Bhavnani, 2014 — Natural vs synthetic differences in breast effects. Supports: Lobuloalveolar differentiation • RANKL pathway • Context-dependent proliferation 5. Synthetic Progestins vs Bioidentical Progesterone Claim: Synthetic progestins differ structurally and bind off-target receptors, producing distinct tissue effects. Core Evidence: Stanczyk et al., 2013 — Receptor binding differences. Sitruk-Ware, 2004 — Biologic comparisons. Chlebowski et al., 2003 (WHI) — Breast cancer signal with CEE + MPA. Supports: Structural divergence • Receptor-level differences • WHI clarification 6. Route of Delivery Differences Claim: Oral, vaginal, transdermal, and sublingual progesterone produce distinct pharmacokinetic profiles and tissue targeting. Core Evidence: Simon, 1995 — Oral vs vaginal PK comparison. Cicinelli et al., 2000 — “First uterine pass effect.” Wren et al., 2003 — Route-dependent systemic levels. Supports: Uterine targeting • Neurosteroid variability • Sedation differences 7. Progesterone, PMS & Migraine Claim: Neurosteroid fluctuations influence GABAergic tone and may contribute to PMS and migraine susceptibility. Core Evidence: Backstrom et al., 2011 — Allopregnanolone fluctuations in PMS. Reddy & Rogawski, 2002 — Neurosteroids and seizure threshold. Martin & Behbehani, 2001 — Hormonal fluctuations and migraine. Supports: Luteal neurosteroid shifts • GABA instability • Migraine association   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.   👇 Tap Subscribe to learn more about what’s actually happening in your body, and what to do about it.   📘 Read Dr. McCarthy’s Book: Jump Off the Mood Swing – A Sane Woman’s Guide to Her Crazy Hormones https://www.amazon.com/Jump-Off-Mood-Swing-Hormones/dp/0999649604   📲 Follow Dr. McCarthy: Instagram: @drbrendanmccarthy TikTok: @drbrendanmccarthy Website: www.protealife.com   💬 Got a question or topic for a future episode? Let us know in the comments!

    28 min

  7. FEB 12

    Progesterone & Breast Health: What Women Were Never Properly Taught

    In this episode of the progesterone series, Dr. Brendan McCarthy — Chief Medical Officer of Protea Medical Center in Tempe, Arizona — explores the often misunderstood relationship between progesterone, estrogen, and breast health. For decades, women have been taught to fear their breasts and fear hormones. While awareness matters, fear is disempowering — and it has left many women confused about what’s actually happening in their bodies. In this episode, we discuss: Why breast tissue is dynamic, not static How estrogen stimulates growth and progesterone restores balance The role of progesterone in breast tissue maturation and architecture Why dense or fibrocystic breasts often reflect unopposed estrogen How restoring ovulation and progesterone can reduce breast pain and density in some women The difference between natural progesterone vs synthetic progestins Where the fear around progesterone and breast cancer really came from Progesterone is not something to fear — it is a hormone of organization, balance, and maturation. Understanding how it works allows women to approach breast health with clarity instead of anxiety. 👍 If this episode was helpful, please like, subscribe, and share it with someone who needs this information. 💬 Comments are read and appreciated. Citations: (Provided for educational purposes; this episode discusses biologic frameworks and observational data, not medical guarantees.) ⸻ Korenman SG. Estrogen window hypothesis (1980) Korenman SG. The etiology of breast cancer: hormone factors. Cancer. 1980;46(4 Suppl):874–880. Context: This paper introduced what later became known as the “estrogen window” hypothesis—the idea that prolonged estrogen-driven proliferation without adequate progesterone signaling may create periods of increased tissue vulnerability. This is a mechanistic framework, not a prevention claim, but it remains foundational in how endocrinologists think about hormonal timing and breast biology. ⸻ Estrogen as a proliferative signal in breast tissue Key TJ, Pike MC. The role of oestrogens and progestagens in the epidemiology and prevention of breast cancer. Eur J Cancer Clin Oncol. 1988;24(1):29–43. Context: Establishes estrogen’s role as a mitogenic (growth-promoting) signal in breast epithelium and frames cancer risk partly in terms of cumulative proliferative exposure over time. ⸻ Progesterone and breast differentiation biology Brisken C, O’Malley B. Hormone action in the mammary gland. Cold Spring Harb Perspect Biol. 2010;2(12):a003178. Context: Describes progesterone’s role in lobuloalveolar development, differentiation, and architectural organization in breast tissue. Supports the concept that progesterone signaling is biologically distinct from estrogen-driven proliferation. ⸻ Fibrocystic breast change and hormonal signaling Sitruk-Ware R. Hormonal replacement therapy and the breast. Menopause. 2002;9(4):237–251. Context: Reviews how different hormonal environments influence benign breast changes, including pain, nodularity, and cystic architecture, and discusses differential tissue effects of estrogen and progesterone signaling. ⸻ Mammographic density and hormonal influence Boyd NF et al. Mammographic density and the risk and detection of breast cancer. N Engl J Med. 2007;356:227–236. Context: Establishes mammographic density as a biologic and radiographic marker influenced by hormonal, stromal, and epithelial factors. Density reflects tissue composition rather than disease itself. ⸻ Bioidentical progesterone vs synthetic progestins (E3N cohort) Fournier A et al. Breast cancer risk in relation to different types of hormone replacement therapy. Int J Cancer. 2005;114(3):448–454. Context: Large observational cohort suggesting that estrogen combined with synthetic progestins was associated with higher breast cancer risk, whereas estrogen combined with micronized progesterone did not show the same risk signal. Observational data—not proof of protection. ⸻ Systematic review: progesterone vs progestins Stute P et al. The impact of micronized progesterone on breast cancer risk. Climacteric. 2018;21(2):111–122. Context: Systematic review concluding that micronized progesterone appears to have a more favorable breast safety profile compared with many synthetic progestins when used in menopausal hormone therapy. ⸻ Endocrine-disrupting compounds and estrogenic signaling Diamanti-Kandarakis E et al. Endocrine-disrupting chemicals: an Endocrine Society scientific statement. Endocr Rev. 2009;30(4):293–342. Context: Summarizes evidence that environmental compounds can exert estrogen-like signaling and disrupt normal hormonal balance, lending plausibility to concerns about prolonged estrogenic exposure without physiologic counter-regulation. ⸻ Important Clarification The research above supports discussion of biologic mechanisms, tissue behavior, and relative risk profiles. It does not establish progesterone as a guarantee against breast cancer, nor does it replace individualized screening, genetics, or oncology care.   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.   👇 Tap Subscribe to learn more about what’s actually happening in your body, and what to do about it.   📘 Read Dr. McCarthy’s Book: Jump Off the Mood Swing – A Sane Woman’s Guide to Her Crazy Hormones https://www.amazon.com/Jump-Off-Mood-Swing-Hormones/dp/0999649604   📲 Follow Dr. McCarthy: Instagram: @drbrendanmccarthy TikTok: @drbrendanmccarthy Website: www.protealife.com   💬 Got a question or topic for a future episode? Let us know in the comments!

    13 min

  8. FEB 5

    Prolactin: The Overlooked Hormone Behind Unexplained Infertility & Low Progesterone

    Unexplained infertility, PMS, and low progesterone are often dismissed when labs fall “within range.” In this episode, Dr. Brendan McCarthy explains why prolactin may be the missing piece. Learn how mildly elevated prolactin can suppress ovulation, lower progesterone, and impact fertility—even when labs appear normal. We also discuss common causes, symptoms, the role of stress and medications, and why diet (including gluten sensitivity) may matter. This episode focuses on precision medicine, not fear—helping you understand what standard reference ranges often miss. Citations: Research — Prolactin and Breast Cancer Risk Below are key epidemiologic and review papers that inform the discussion in this episode regarding prolactin and breast biology. These studies look at associations, not simple cause-and-effect relationships, and help explain why prolactin shows up in breast health conversations. Meta-analysis: circulating prolactin and breast cancer risk Wang M, et al. (2016). Plasma prolactin and breast cancer risk: a meta-analysis. Cancer Causes & Control. This meta-analysis pooled data from multiple observational studies comparing women with higher versus lower circulating prolactin levels. Across studies, higher prolactin levels were associated with a modest but statistically significant increase in breast cancer risk. The association was most evident in postmenopausal women and in hormone-receptor–positive tumors. This helps explain why prolactin is considered a relevant growth signal in breast tissue rather than just a “lactation hormone.” Systematic review and meta-analysis: prolactin levels across breast cancer cohorts Aranha AF, et al. (2022). Impact of prolactin levels in breast cancer: a systematic review and meta-analysis. Endocrine-Related Cancer. This more recent systematic review and meta-analysis evaluated circulating prolactin levels across breast cancer populations and control groups. Elevated prolactin levels were associated with higher breast cancer occurrence, with stronger associations seen in invasive cancers and hormone-receptor–positive disease. This paper adds weight to the idea that prolactin participates in breast biology in ways that matter clinically, even outside of pregnancy and breastfeeding. Prospective cohort studies: prolactin measured before diagnosis Tworoger SS, et al. (2004; 2006). Prospective analyses from large cohorts including the Nurses’ Health Study. In these studies, prolactin was measured years before any breast cancer diagnosis. Women with higher prolactin levels had a higher likelihood of developing breast cancer later, particularly estrogen-receptor–positive tumors in postmenopausal women. Because prolactin was measured before cancer developed, these studies help clarify timing and reduce the concern that elevated prolactin is simply a consequence of disease. Mechanistic context (supportive background) Experimental and translational studies show that prolactin receptor signaling influences mammary epithelial cell growth, differentiation, and interaction with estrogen signaling pathways. This provides a biologic backdrop for why epidemiologic associations between prolactin and breast cancer risk keep appearing across different study designs. How to read this as a clinician or patient These data do not mean prolactin “causes” breast cancer in a simple or deterministic way. What they do show is that prolactin is an active hormone in breast tissue, and chronically higher levels are consistently associated with changes in breast risk profiles across large populations. That’s why prolactin deserves attention in conversations about fertility, breast symptoms, and long-term hormonal signaling—not fear, and not dismissal.    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.   👇 Tap Subscribe to learn more about what’s actually happening in your body, and what to do about it.   📘 Read Dr. McCarthy’s Book: Jump Off the Mood Swing – A Sane Woman’s Guide to Her Crazy Hormones https://www.amazon.com/Jump-Off-Mood-Swing-Hormones/dp/0999649604   📲 Follow Dr. McCarthy: Instagram: @drbrendanmccarthy TikTok: @drbrendanmccarthy Website: www.protealife.com   💬 Got a question or topic for a future episode? Let us know in the comments!

    15 min
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24 Ratings

About

Welcome! Dr. Brendan McCarthy founded Protea Medical Center in 2002. While he’s been the chief medical officer, Protea has grown and evolved into a dynamic medical center serving the Valley and Central Arizona. Through successful case after successful case, Dr. McCarthy has been dedicated to hormone balance, healthy metabolism, and the best quality of life. Dr. McCarthy’s hallmark is his unorthodox approach to mental/emotional wellness and its link to hormone balance in women and men. Through the use of blood work and clinical investigation, Dr. McCarthy gets to the bottom of possible causes for common conditions such as anxiety, PMS, depression, slow metabolism, weight gain, insomnia and now wants to share his knowledge to the viewers with his podcast. Join the discussion, ask questions, and welcome to the podcast!

Information

  • Creator
    Dr. Brendan McCarthy
  • Years Active
    2023 - 2026
  • Episodes
    177
  • Rating
    Clean
  • Copyright
    © Copyright 2023 All rights reserved.
  • Show Website
    Dr. Brendan McCarthy

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