Explore Dr. Retzler’s HormoneSynergy® Longevity Medicine Resource Library

Longevity Medicine, Functional Wellness & Anti-Aging Insights from HormoneSynergy®

Welcome to the HormoneSynergy® Longevity Medicine Blog, a physician-guided clinical library led by Dr. Kathryn Retzler. Our articles cover the systems that most often shape health with age: metabolic health, hormones, cardiovascular and kidney risk, body composition, bone and muscle, brain health, sleep, gut health, nutrition, supplements, and the biology of aging.

The library is organized around clinical questions rather than trends. Some articles review new research. Others explain testing, treatment, nutrition, or a condition patients commonly encounter. Across the collection, the standard is the same: evidence first, appropriate uncertainty, and enough clinical context to separate useful medicine from wellness marketing.

Start with the HormoneSynergy® Longevity Medicine Framework

New & recently updated:

Metabolic Health & Insulin Resistance

Clinical resources on insulin resistance, glucose regulation, metabolic syndrome, visceral fat, prediabetes, obesity and GLP-1-based care within a broader longevity medicine plan.

Kidney Health & Cardiovascular-Kidney-Metabolic Health

Kidney health belongs in the same clinical conversation as blood pressure, diabetes, insulin resistance, obesity and cardiovascular risk. These resources cover early detection, CKD, albuminuria, nutrition and CKM health.

Gut Health, Microbiome & Immune Signaling

Clinical education on the microbiome, intestinal barrier, fiber, inflammation, gut-brain signaling, immune biology and the growing connections between gut, metabolic and kidney health.

Food Quality, Vitamins, Supplements & Wellness Claims

Evidence-based guidance on nutrient gaps, supplement quality, interactions, food claims and longevity products, with an emphasis on where supplementation helps and where marketing outruns the evidence.

  • Iron Supplements — When You Need Them, When You Don’t, and Why Testing Comes First

    Iron deficiency testing with ferritin, hemoglobin and transferrin saturation before starting iron supplements

    Iron deficiency is common, but fatigue alone is not a reason to start an iron supplement. Ferritin, hemoglobin, transferrin saturation, menstrual history, gastrointestinal health and the reason iron is low all influence treatment. Here is when iron helps, when it can cause problems, and why unexplained deficiency deserves an evaluation.

  • Predatory Wellness, “Detox,” and GLP-1 Myths

    A patient compares an elaborate detox program and GLP-1 claims with a physician’s explanation of normal detoxification and metabolic physiology.

    Detox marketing often begins with familiar symptoms and ends with a proprietary sequence of cleanses, supplements, coaching, testing, and affiliate products. This editorial examines how ordinary physiology is repackaged as an invisible disorder, how GLP-1 concerns are recruited into the same sales funnel, and why the theory becomes difficult to disprove.

  • Pendulum Akkermansia vs. Akkermansia 500 PRO: Same Strain, Different Dose

    Pendulum Akkermansia and Akkermansia 500 PRO compared side by side for gut microbiome support and targeted Akkermansia supplementation.

    Pendulum Akkermansia and Akkermansia 500 PRO contain the same live strain and the same prebiotic fiber. The important difference is dose: 100 million versus 500 million AFU. Here is what that difference means, and what the research does not yet tell us.

  • NAC, Glutathione and Alcohol: What the Newer Research Says About Liver Protection and Timing

    NAC, glutathione, alcohol metabolism and liver antioxidant defenses showing acetaldehyde, oxidative stress and hepatic redox biology.

    An older mouse study suggested that NAC could protect the liver before alcohol yet worsen injury when given several hours afterward. Later research makes the story more complicated. Glutathione biology appears important to liver resilience, NAC is used clinically in severe alcohol-associated hepatitis, and newer animal and human studies do not support a simple rule that NAC is beneficial before alcohol and harmful afterward.

  • Can Nearly Half of Dementia Cases Be Prevented? What the Research Actually Shows

    Older couple overlooking a branching Pacific Northwest river delta that subtly resembles the structure of the brain.

    The latest research suggests that a substantial share of dementia may be delayed or prevented by addressing cardiovascular, metabolic, sensory, and lifestyle risks across the lifespan. The widely quoted 45% figure is encouraging, but it requires careful interpretation.

  • I’m a German Shepoodle, and I Get More Massages Than Most Humans: The Therapeutic Benefits of Massage

    Aria, a furry black German Shepoodle, relaxing belly-up while receiving a gentle therapeutic massage.

    Aria sets the record straight about her German Shepherd and Standard Poodle heritage, then considers why dogs receive daily rubs while humans treat therapeutic massage like an occasional luxury.

  • Muscle Matters. But Longevity Is Bigger Than Muscle.

    Muscle and longevity shown within a broader healthy-aging strategy including strength, cardiovascular fitness, body composition, metabolic health and nutrition.

    Muscle deserves far more attention in preventive medicine. Strength, lean mass and adequate protein all become increasingly important with age. But longevity is not a competition to build the most muscle or eat the most protein. Cardiovascular fitness, visceral fat, bone, metabolic health, sleep, cognition and the quality of the overall diet remain part of the same physiology.

  • Obstructive Sleep Apnea: The Overnight Health Risk Many People Never Recognize

    Man sleeping on his back with medical overlays showing upper-airway obstruction, reduced oxygen, brain activity and cardiovascular stress.

    Obstructive sleep apnea repeatedly interrupts breathing, oxygen delivery and normal sleep architecture. Its effects extend beyond snoring and fatigue, influencing blood pressure, heart rhythm, glucose regulation, cognitive function, mood and long-term cardiovascular risk.

  • Does Sleep Position Matter? What Back, Side and Stomach Sleeping May Reveal About Your Health

    Man sleeping on his back and woman sleeping on her side, illustrating how sleep position may affect breathing, reflux and musculoskeletal comfort.

    Men often report sleeping on their backs, while women more commonly describe sleeping on their sides or stomachs. Research suggests that the difference is less consistent than it appears, but sleep position can still provide useful information about breathing, reflux, pregnancy, pain and cardiovascular symptoms.

  • Can a Naturopathic Physician Prescribe Medication? What Oregon Law Actually Says

    Licensed naturopathic physician in a clinical setting with Oregon, Washington, Arizona, Vermont and Maine highlighted as examples of differing state laws governing naturopathic physician licensure and prescribing authority.

    Confusion about naturopathic physicians often begins with a problem few people realize exists: not everyone using the letters “ND” has graduated from an accredited naturopathic medical school or qualifies for medical licensure. In Oregon, licensed naturopathic physicians are legally recognized physicians within their profession, are trained in conventional medical sciences, and have broad prescription authority that can include controlled substances. Here is what Oregon law actually says.

  • Visceral Fat: Why It Matters More Than BMI and What a DEXA Scan Can Show

    Visceral fat and DEXA body composition illustration showing abdominal VAT, lean mass and metabolic health assessment by HormoneSynergy®.

    Visceral fat can increase cardiometabolic risk even when body weight and BMI appear normal. Learn how HormoneSynergy® uses Hologic® DEXA, metabolic testing, hormone evaluation, and muscle assessment to put visceral fat into clinical context.

  • DAO and Histamine Intolerance: What Diamine Oxidase Can and Cannot Tell You

    DAO and histamine intolerance article explaining diamine oxidase, dietary histamine metabolism, diagnosis and DAO supplementation.

    Diamine oxidase, or DAO, helps metabolize histamine from food within the intestinal tract. Supplemental DAO may be useful for some people with reproducible food-related histamine symptoms, but histamine intolerance remains difficult to diagnose and is frequently oversimplified. Here is what the physiology and clinical evidence actually support.