The Human Upgrade with Dave Asprey

Episode 1434: Here's Why You Still Feel Like Sh*t After Doing Everything Right...
Guest: McCall McPherson, PA-C (Founder, Modern Thyroid Clinic)
Date: March 19, 2026

Episode Overview

This episode dives deep into the pervasive but often misunderstood and misdiagnosed problem of thyroid dysfunction. Dave Asprey and foremost thyroid specialist McCall McPherson unravel why so many people still feel fatigued, foggy, or struggle to lose weight—despite “doing everything right.” They dissect the shortcomings of conventional thyroid testing, the nuances of thyroid hormone management, lifestyle and environmental contributors, and actionable insights for anyone seeking better energy, mood, and longevity.

Key Discussion Points & Insights

1. Personal Thyroid Journeys

• Dave Asprey shares his own story—being told at 26 that his testosterone was lower than his mother’s and his thyroid was “almost undetectable.” Proper thyroid treatment was life-changing:

  "It was like someone turned the lights back on. I just felt my body relax, and didn't realize how much effort I was spending on everything I did." (00:44)

• McCall McPherson recounts her struggle as a young clinician on Synthroid, bedridden with classic hypothyroid symptoms until comprehensive testing and the right medication restored her life.

  "I was spending 16 hours a day in bed, overweight, hair was falling out, depressed, couldn't function... Saw an integrative doc and got my life back in a couple months." (04:34–05:37)

2. Why Most Thyroid Care Fails

• Conventional medicine typically tests for TSH only, missing the real picture.
• Symptoms like fatigue, depression, weight gain, and hair loss are dismissed if TSH is "normal."
• Inadequate testing leads to underdiagnosis and undertreatment, especially for women and postpartum moms.
• McPherson:

  "Medicine is working overtime now on treating less and less. Now, doctors are told not to treat until TSH is over 10, sometimes 20! That's crazy." (09:39)

3. How Thyroid Hormones Work (Simplified)

• TSH (from brain) stimulates the thyroid to make T4 (“crude oil”), which must be converted to T3 (“gasoline”) for active metabolic effects.
• Many only check TSH and T4.
• Reverse T3 (inactive form) can block real T3 action.
• McPherson:

  "TSH and T4 reflect variations in your T3 only 1-2% of the time... It doesn't give you the full picture." (08:41)

4. The Thyroid–Psychiatry Connection

• Many psychiatric symptoms—especially “treatment-resistant depression”—are often undiagnosed thyroid issues.
• Standard psychiatry ignores thyroid optimization.
• McPherson:

  "Huge mood disruption... people aren't really responding until their TSH is much, much lower than medicine calls for." (06:28)

5. Women, Postpartum, and Hormonal Vulnerability

• Women (especially those with children) are at much higher risk—up to 9x more than men.
• Pregnancy, postpartum, and menopause are critical windows for onset of thyroid autoimmunity.
• “If you’re a woman and a mother, it’s not if, but when you get thyroid issues.” (11:49)
• Men also affected, but often dismissed or less in-tune.

6. Diet, Environment & Toxins

• Fluoride in water and toothpaste, bromine in American wheat, and environmental toxins directly suppress thyroid—well-documented since 1945. (22:00, 28:25–28:55)
• Gluten (wheat), dairy, mold exposure, and sometimes legumes, grains, and high-oxalate foods provoke immune dysfunction and can trigger Hashimoto’s and hypothyroidism.

• "The two things most likely to cause Hashimoto's are mold and wheat. Dairy's a big one, too." (23:19)

• Water and air filters are recommended first steps for those on a health journey.

7. Why “Eat Less, Exercise More” Doesn’t Work

• With low thyroid, caloric restriction, over-exercise, or clean eating will NOT help weight loss, even with superhuman effort.

• "90 minutes a day, six days a week...never lost an inch or a pound... Doctors thought I was lying." (12:56)

• Clinicians often don’t believe patients, especially women.

8. Testing & Lab Interpretation

What Is a Full Thyroid Panel? (20:01)

• TSH

• Free T4

• Free T3

• Reverse T3

• Thyroid antibodies (Thyroid Peroxidase & Thyroglobulin antibodies)

• Direct-to-consumer labs now allow easier access; doctors reluctant to order comprehensive panels often won’t know how to interpret them.

• Lab ranges do NOT reflect optimal health, just the average sick population:

  "Normal is not okay in the US right now. You do not want to be normal." (50:01)

Optimal Lab Ranges (31:19)

• TSH: Around 1, never above 1.8
• Free T4: 0.9 – 1.2
• Free T3: 3.6 – 4.2 (timing of the test and medication affects readings)

9. Treatment: Why Synthroid and T4 Alone Often Fail

• Most get prescribed levothyroxine (Synthroid, T4), but many cannot convert T4 to T3, so they stay symptomatic.
• All McPherson’s patients are on some form of T3.

  "I don't think there's a place [for T4 only] in our practice... everyone's needs are different and it's based on their biochemistry." (15:52)

• Natural desiccated thyroid (glandular), T3, synthetic mixtures, or combos tailored to the individual work better.
• Optimal treatment is bio-individual, not one-size-fits-all.

10. Thyroid, Sex Hormones, and Libido

• Low thyroid directly reduces libido in both men and women—AND lowers testosterone, which further disrupts sex drive and motivation.

  "Low T is the first hormone dysfunction to show up with hypothyroidism... 99.5% of our patients have testosterone extraordinarily low." (29:54–30:22)

• Treat thyroid before trying to "fix" testosterone or estrogen alone.

11. Autoimmunity & Remission

• Hashimoto’s (autoimmune thyroiditis) often co-exists with other autoimmune diseases.
• If you reduce thyroid antibodies (via logic-based diet, treating celiac, removing mold, and proper therapy), you can reduce risk for more serious autoimmunity.
• McPherson:

  "I'm completely in remission. I've been in remission for over a decade." (21:42)

12. Supplements, Diet, and Non-Hormonal Supports

• Key nutrients for thyroid conversion: zinc, selenium, magnesium, ashwagandha, good iron status.
• Removing inflammatory foods—gluten, dairy, legumes, grains, sometimes nuts/seeds.
• Vitamin D deficiency is the norm, even for outdoor workers.
• Tyrosine (precursor for thyroid and dopamine): promising, supported by expert data (Isabella Wentz).
• Circadian health and sleep matter, but are likely secondary to proper diagnosis and medication.
• Oxalates (plant antinutrients) may contribute to mitochondrial and thyroid dysfunction, especially in high “health food” diets.

13. Myths & Medical System Issues

• Medical resistance to T3:

  "We're trained: do not use T3, only use T4. If you use T3, you're going to give your patients a heart attack or a stroke." (60:43) "Higher levels of T3 decrease mortality... higher levels of T4 increase it, but medicine teaches the opposite." (60:55)

• Labs vary by location and reference range—don't trust “within normal limits” if you feel bad.

14. The Real-Life Impact of Treating Thyroid

• Improved mood, less irritability, restored energy, relationships, and even career outcomes.
• Greater employment stability, higher income, and less early retirement among those with optimized T3.
• Profound improvement in generational family dynamics, marriage, and overall longevity.

Notable Quotes & Memorable Moments

• "If someone hadn't helped me, I would be on disability by now. I really believe that." (14:08)
• "So maybe it's not treatment-resistant depression. They just don't know how to treat it." – Dave Asprey (06:54)
• "If you get all the supplements but your thyroid's off, you’re still gonna feel like shit." (64:16)
• "You want to be superhuman. What would a vibrantly healthy 25- or 30-year-old look like? That's what you want to do." (50:01)
• "It's not your husband's fault anymore ... or at least not everything's your husband's fault." – McCall McPherson (47:11)
• "Biohacking is complex... But the lowest hanging fruit—get your labs, check thyroid, and sex hormones." (64:16)

Timestamps for Important Segments

• Personal stories: 00:00–06:25
• Thyroid basics & why current testing fails: 07:03–10:46
• Psychiatric symptoms and the thyroid: 06:25–07:03, 48:54–49:47
• Women's thyroid risk & pregnancy: 11:49–12:56
• Food/environmental causes: 21:42–24:19, 27:47–29:50
• Why T4-only meds fail: 14:24–15:52
• Anti-thyroid toxins in water, food: 28:20–29:50
• Lab test recommendations: 20:01, 31:19, 50:01
• Lab “normals” are misleading: 50:01–51:18
• Thyroid & libido/testosterone: 29:54–31:19
• Supplements & cofactors: 40:51–41:38, 53:58–54:58
• Vitamin D & thyroid: 55:54–57:46
• Circadian light & thyroid: 57:52–59:46
• Myths about T3 danger: 60:43–63:40
• Downstream effects of treatment: 46:34–48:05
• Modern Thyroid Clinic info: 65:30

Actionable Takeaways

• Get a full thyroid panel: Don’t settle for TSH alone—test Free T4, Free T3, Reverse T3, and antibodies.
• Work with someone who understands bio-individuality: Optimal levels are tighter, and treatment plays with both T3 and T4 as needed.
• Remove environmental disruptors: Filter water, avoid fluoride/bromine, test for mold; cut gluten and dairy to see impact.
• Support with co-factors: Zinc, selenium, magnesium, ashwagandha, vitamin D, tyrosine.
• Don’t accept “normal range” if you’re symptomatic. Push for optimal, not average, and self-advocate.
• Understand chronic symptoms might be your thyroid—even if you’ve “done everything right.”

Resources Mentioned

• Modern Thyroid Clinic
• Axo Health (for direct-to-consumer labs)
• Lab ranges and resources (Dave’s page with numbers and notes)
• Moldymovie.com (Dave’s documentary on toxic mold)

Episode Tone

Supportive, myth-busting, and practical; focused on empowering listeners—especially women—to trust their symptoms, test thoroughly, and demand better care.

For anyone stuck with persistent symptoms despite “optimizing everything,” thyroid function is foundational—get it right before chasing other solutions.