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.

  • Exercise, Sleep, Sitting, and Dementia Risk: The Basics Are Not Optional

    Older adult walking outdoors with subtle brain-health and sleep imagery, representing the connection between movement, sleep, sedentary time, and dementia risk in longevity medicine.

    New research adds to a growing body of evidence that movement, sleep, and less sedentary time are central to brain health. Dementia prevention is not about one supplement or one scan. It is about reducing cumulative risk across the systems that keep the brain resilient.

  • Dangerous “Natural” Supplements: What Feel Free Teaches Us About Kratom, Kava, and Wellness Marketing

    Editorial medical image showing generic wellness tonic bottles under a frosted-glass caution overlay, representing dangerous natural supplements, kratom, kava, and supplement marketing risks.

    Some products are marketed as natural, plant-based, or alcohol alternatives, but that does not mean they are safe. Feel Free is a useful example of why supplement marketing needs clinical context, especially when products affect the brain, nervous system, mood, pain, sleep, or dependence pathways.

  • Birding, Brain Health, and Longevity: Why Paying Attention to Nature May Help Protect the Aging Brain

    Backyard bird habitat with birds, native plants, and a subtle brain-network overlay representing birding, attention, memory, and cognitive longevity.

    Birding is more than a quiet hobby. New brain imaging research suggests that expert birders may develop measurable differences in brain regions involved in attention, visual processing, memory, and object recognition. The finding does not prove that birdwatching prevents dementia, but it supports something longevity medicine has long recognized: the brain is shaped by how we use it.

  • TPO Antibodies, Hashimoto’s, and Thyroid Autoimmunity: What This Test Actually Tells You

    Educational clinical graphic showing thyroid antibody testing, TPO antibodies, thyroid function markers, and autoimmune thyroid evaluation in longevity medicine.

    High TPO antibodies can identify autoimmune thyroid disease, most commonly Hashimoto’s, but they do not tell you whether the thyroid is failing. Learn what positive TPO antibodies mean, what to do when TSH is normal, whether antibodies need to be repeated, and what the evidence says about selenium, vitamin D, gluten, pregnancy, and treatment.

  • Peptides and Longevity Medicine: FDA-Approved Drugs, Compounded Gray Zones, and Anti-Aging Hype

    Injectable peptides, FDA-approved drugs, compounded gray zones, and anti-aging marketing reviewed through a clinical longevity medicine lens at HormoneSynergy®.

    Peptides are not one thing. Some are FDA-approved medications with specific indications. Others are compounded, investigational, or marketed as anti-aging injections despite limited safety and outcome data. The distinction matters.

  • Molecular Hydrogen, Anti-Aging Claims, and Wellness Marketing: When an Interesting Molecule Becomes a Miracle Cure

    Molecular hydrogen anti-aging claims reviewed through an evidence-based longevity medicine lens at HormoneSynergy®.

    Molecular hydrogen is biologically interesting, and early research suggests possible effects on oxidative stress, inflammation, metabolism, and recovery. But “miracle molecule” claims that promise to reverse aging or chronic disease have moved far ahead of the evidence.

  • Pet Ownership, Grief, and Longevity: What Dogs Teach Us About Health, Rhythm, and Survival

    A man walking with a black German Shepherd on a quiet path, representing pet ownership, companionship, movement, grief, cardiovascular health, and longevity medicine.

    After losing my black German Shepherd, Onyx, to hemangiosarcoma, I found myself thinking about what dogs really do for our health. The science suggests pet ownership, especially dog ownership, may be associated with longer life and lower cardiovascular risk. But the deeper truth is not just about walking more steps. It is about routine, connection, purpose, grief, and the way an animal can become part of our nervous system.

  • Skin Care in Longevity Medicine: Cancer Prevention, Wrinkles, Retinoids, and the Biology of Aging Skin

    Female physician reviewing a skin health scan with a patient, with visual cues for UV exposure, collagen, skin barrier function, inflammation, and skin cancer prevention in longevity medicine.

    Skin care is not just about looking younger. In longevity medicine, skin reflects UV exposure, collagen remodeling, inflammation, hormones, metabolic health, barrier function, and cancer risk.

  • EMF Sensitivity, Wi-Fi Symptoms & EMF Protection Devices: What the Science Shows

    EMF sensitivity, Wi-Fi exposure and EMF protection wearables including pendants, bracelets and phone stickers reviewed by HormoneSynergy Longevity Medicine.

    Headaches, brain fog, poor sleep, and fatigue are sometimes blamed on Wi-Fi, cell phones, smart meters, Bluetooth, or 5G. The symptoms can be very real, but controlled studies have not shown that ordinary low-level radiofrequency exposure reliably causes them. We look at electromagnetic hypersensitivity, the latest evidence, and the booming market for EMF pendants, stickers, bracelets, chips, and “harmonizers.”

  • Fake Doctors, AI Health Groups, and Wellness Marketing: How Patients Can Protect Themselves Online

    HormoneSynergy Longevity Medicine educational graphic about fake doctors, AI health groups, and wellness marketing, emphasizing real credentials, clinical judgment, and patient protection online.

    AI-generated health pages, fake doctor accounts, anonymous symptom groups, and miracle wellness funnels are becoming harder to distinguish from real medical guidance. Here is how patients can protect themselves online without becoming cynical, fearful, or disconnected from real care.

  • EMF, Mast Cells, and MCAS: What Science Actually Shows

    Clinical editorial image representing electromagnetic field exposure, mast-cell activation, nervous-system sensitivity, inflammation, and longevity medicine evaluation.

    Some people with mast-cell symptoms wonder whether Wi-Fi, phones, smart meters, or other electromagnetic fields are triggering their reactions. The biology is plausible enough to study, but the human evidence is not strong enough to call everyday EMF exposure a proven cause of MCAS.

  • Clove Oil, Methylene Blue, and Cancer Claims: When Mechanistic Research Becomes Wellness Marketing

    Clinical illustration of mechanistic cancer research being separated from wellness marketing claims

    Clove oil nanoemulsions and methylene blue have both been studied in early cancer-related research. But cell studies and mechanistic findings are not the same as safe, effective cancer treatment in humans.