From time to time, Dr. Kara Fitzgerald invites selective guest contributors to submit content for publication on her website that aligns with her vision and mission, and high standards for quality and scientific rigor.

Dr. Kara Fitzgerald blog graphic titled “FSH Testing in Perimenopause: Why One Test Isn’t Enough,” with hormone trend lines and a brain illustration.

FSH Testing in Perimenopause: Why One Test Isn’t Enough

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FSH is having a quiet moment in longevity medicine — though most of us have not noticed yet. Follicle-stimulating hormone is still treated, in most practices, as a simple yes-or-no test: ordered once, or at most twice, to confirm menopause (or evaluate fertility), then set aside. But a growing body of research is reframing FSH as something more interesting: a longitudinal signal that may track how a woman’s bone, muscle, brain, and metabolism are aging. These are the very tissues we now think of as longevity organs. If that reframe holds, then the way most of us use FSH is leaving a great deal of information on the table.

Illustration of protein and gut microbes above the intestinal lining, representing protein digestion, the microbiome, and muscle health.

Why More Protein Isn’t Always the Answer

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Protein continues to be a hot topic in nutrition and longevity medicine. Much of that interest stems from the growing recognition that skeletal muscle is a longevity organ that influences metabolism, mitochondrial function, immune regulation, and cognitive health. As a result, maintaining muscle mass and function has become a cornerstone of healthy aging, and clinicians are increasingly encouraging patients to consume more protein.

Lion’s Mane mushroom and the title “One Mushroom. Two Patients.” for a Dr. Kara Fitzgerald blog on targeted Lion’s Mane formulations.

One Mushroom, Two Patients: A Practitioner’s Case for Targeted Lion’s Mane Formulation

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There’s a question worth asking every time you prescribe Lion’s Mane: which patient are you prescribing it for? Most integrative practitioners already use Lion’s Mane, but few consider the variables. Raw material, preparation type, extract, and dose all affect therapeutic outcomes. To confound matters further, the market positioning of Lion’s Mane tends to be a poor reflection of both tradition and clinical research. The clearest example is that it gets labeled as a nootropic, something anyone might use for sharper thinking. That framing attracts consumers, but it does not hold up in clinic.

A woman looking out a sunlit window surrounded by imagery representing fertility, mitochondria, and reproductive health, illustrating a holistic approach to fertility preservation beyond egg freezing.

Fertility Preservation Beyond Egg Freezing

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A 31-year-old patient sits across from me and says, “My friends are all freezing their eggs. Should I be doing that too?” It is a question I hear constantly. And while oocyte cryopreservation is a legitimate tool for specific situations, the way it is being marketed has created a damaging assumption: that fertility is a fixed, steadily declining resource that technology must eventually rescue.

Older woman lifting a dumbbell with muscle anatomy illustration behind her, representing strength training and healthy aging.

Why Muscle Strength Is the #1 Predictor of Healthy Aging

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There’s one metric that consistently predicts how well we age, and it’s finally showing up in the conversations that matter. It’s not blood pressure, cholesterol, or BMI. It’s muscle strength. Muscle health plays a central role in healthy aging, influencing mobility, quality of life, and metabolic health. Yet historically, strength has been viewed primarily through the lens of fitness or performance rather than as a core clinical target.

Beyond fiber quantity: the role of fiber diversity in shaping the gut microbiome

Beyond fiber quantity: the role of fiber diversity in shaping the gut microbiome

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More than 90% of women and 97% of men in the US fall short of recommended fiber intake. The standard American diet lacks the overall fiber content that each of us need to maintain health. But, this gap is not only about quantity; there’s also a significant gap in fiber diversity. There is evidence that fiber quality and diversity are critical because different types of fiber are metabolized by different gut bacteria, producing a variety of short-chain fatty acids (SCFAs) and downstream effects on gastrointestinal and metabolic health.

Heat and Light as Medicine: What Research Shows About Infrared Therapy, Cardiometabolic Health, and Longevity

Heat and Light as Medicine: What Research Shows About Infrared Therapy, Cardiometabolic Health, and Longevity

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Functional medicine often focuses on nutrition, exercise, and stress management as the foundational pillars of health. But what other powerful environmental inputs could be leveraged with greater precision? What if heat and light could be used as biological inputs in a way that is measurable and clinically relevant?

How Helping Older Dolphins Unlocked A Secret To Healthy Aging

How Helping Older Dolphins Unlocked A Secret To Healthy Aging

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Did you know that 1 in 3 older dolphins develops the same aging-associated conditions as humans? While continually helping to improve the health of older Navy dolphins living in San Diego Bay, veterinarians found that some dolphins had elevated cholesterol, insulin resistance, chronic inflammation, and fatty liver disease – just like some of us.

Urolithin A for mitochondria and immune health

Human Clinical Evidence Supporting High-Dose Urolithin A for Mitochondrial and Immune Function

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Age-related declines in muscle function, immune resilience, and cellular energy are closely linked to mitochondrial dysfunction, making mitochondrial-targeted interventions a key focus of aging research. In this context, recent placebo-controlled human trials show that a Urolithin A dose of 1000 mg produces broader and more pronounced effects on mitochondrial gene expression, muscle performance, and immune markers than lower doses.