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.

  • Inflammation and Atherosclerosis: What Actually Drives Plaque and Cardiovascular Risk

    Inflammation and heart disease showing how chronic inflammation contributes to atherosclerosis plaque development and cardiovascular risk HormoneSynergy® Longevity Medicine Portland • Lake Oswego • USA

    Atherosclerosis is both a lipoprotein-retention disease and an inflammatory disease of the arterial wall. ApoB-containing particles help initiate plaque, while inflammation influences plaque growth, vascular injury and the events that can ultimately lead to heart attack or stroke.

  • CIMT Ultrasound: Measuring Arterial Plaque Before Symptoms

    Coronary CT angiography detecting coronary artery plaque and cardiovascular risk HormoneSynergy Longevity Medicine Portland Lake Oswego USA

    Carotid intima-media thickness (CIMT) ultrasound is a non-invasive imaging test that evaluates the thickness of the carotid artery wall and can help detect early signs of atherosclerosis before symptoms appear.

  • Body Fat Percentage and Health Risk: What Is Optimal?

    Visceral fat versus subcutaneous fat illustrating differences in metabolic risk insulin resistance and cardiovascular disease HormoneSynergy® Longevity Medicine Portland • Lake Oswego • USA

    Body fat percentage provides a more accurate picture of metabolic and cardiovascular risk than body weight alone. Understanding healthy body fat ranges helps identify risk earlier and guide strategies for metabolic health and longevity.

  • Intestinal Permeability and “Leaky Gut”: What the Science Actually Shows

    Medical illustration showing intestinal epithelial cells, tight junctions, the mucus layer, and a localized area of increased permeability.

    “Leaky gut” is not imaginary. Increased intestinal permeability is a real and measurable change in intestinal barrier function and is documented in a number of gastrointestinal and systemic conditions. What becomes problematic is using “leaky gut syndrome” as a catch-all diagnosis for bloating, fatigue, brain fog, food reactions, inflammation, or almost any chronic symptom. Here is what we know about the intestinal barrier, what can disrupt it, how it is evaluated, and what may help restore normal barrier function.

  • Butyrate and Gut Health: Why Short-Chain Fatty Acids Matter

    Female physician reviewing butyrate, short-chain fatty acids, fiber intake, gut barrier integrity, microbiome diversity, inflammation, and metabolic health with a patient at HormoneSynergy® Longevity Medicine in Portland and Lake Oswego.

    Butyrate is a short-chain fatty acid produced by beneficial gut bacteria during the fermentation of dietary fiber. It plays an important role in supporting intestinal barrier function, immune signaling, and metabolic health.

  • Akkermansia muciniphila: Gut Barrier, Metabolism and the Microbiome

    Akkermansia muciniphila beneficial gut bacteria supporting intestinal barrier health metabolic function and longevity HormoneSynergy® Longevity Medicine Portland • Lake Oswego • USA

    Akkermansia muciniphila lives within the intestinal mucus layer and has become one of the most closely studied organisms in microbiome research. Here is what we know about its relationship with the gut barrier, metabolism and long-term health, and where the science remains unsettled.

  • The Gut-Brain Axis: How the Microbiome Influences the Brain

    Gut–brain axis illustrating how the gut microbiome influences brain function mood cognition and inflammation HormoneSynergy® Longevity Medicine Portland • Lake Oswego • USA

    The gut-brain axis describes the communication network connecting the digestive system and the brain. Signals between gut bacteria, intestinal cells, the immune system, and the nervous system influence metabolism, mood, and neurological function.

  • How Insulin Resistance Leads to Heart Disease

    Insulin resistance contributing to heart disease and metabolic dysfunction HormoneSynergy Longevity Medicine Portland Lake Oswego USA

    Insulin resistance is closely linked to cardiovascular disease through its effects on inflammation, cholesterol metabolism, blood pressure regulation, and arterial plaque formation. Understanding this connection helps explain why metabolic health is central to preventive cardiology and longevity medicine.

  • DEXA Body Composition Scan: What It Measures and Why It Matters

    DEXA scan measuring body composition including muscle fat and bone density HormoneSynergy Longevity Medicine Portland Lake Oswego USA

    A DEXA body composition scan provides detailed information about fat mass, lean muscle mass, bone density, and visceral fat distribution. These measurements help evaluate metabolic health, physical performance, and long-term health risk within a preventive longevity medicine framework.

  • Sarcopenia and Healthy Aging: Muscle Loss, Strength, and Metabolic Health

    Older adult resistance training with skeletal muscle and body composition graphics illustrating sarcopenia, strength, metabolic health, and healthy aging.

    Sarcopenia involves more than losing muscle with age. Strength, muscle quantity, physical performance, nutrition, resistance training, and body composition all influence the risk of declining mobility and independence.

  • Muscle Mass and Longevity: Why Strength Predicts Healthspan

    Active adults strength training with skeletal muscle, grip strength, glucose metabolism, and body composition graphics illustrating muscle mass and longevity.

    Muscle is more than tissue for movement. It helps regulate glucose, provides physical reserve during illness and aging, and supports the strength needed to remain independent. Muscle quantity matters, but strength and physical performance often tell us even more.

  • Gut Health and Metabolic Disease: The Microbiome-Insulin Resistance Connection

    Gut microbiome and intestinal barrier connected with insulin signaling in the pancreas, liver, skeletal muscle, and visceral fat.

    The gut microbiome may influence insulin sensitivity through microbial metabolites, intestinal-barrier function, immune signaling, bile acids, and gut hormones. The relationship is biologically credible, but metabolic disease also reshapes the microbiome. This article separates what is established from what remains under investigation.