Summary
A thyroid specialist from the Modern Thyroid Clinic joins Dave Asprey to explain why so many people still feel terrible despite doing everything right, often because of undiagnosed or undertreated thyroid dysfunction. They cover the full thyroid signaling pathway from TSH to free T4 and T3 conversion, why standard lab panels miss the problem, and how fluoride, bromine, and other environmental factors suppress thyroid function.
Key Points
- Standard TSH-only panels miss thyroid dysfunction because TSH can be "normal" while free T3 (the active hormone) is low.
- A complete thyroid panel should include TSH, free T4, free T3, reverse T3, and thyroid antibodies (TPO and TG).
- Fluoride, bromine, and chlorine compete with iodine for thyroid receptor binding, suppressing hormone production.
- Poor T4-to-T3 conversion is often caused by gut inflammation, low selenium, high cortisol, or caloric restriction.
- Many patients on levothyroxine (T4-only medication) still feel poorly because they need added T3 for symptom resolution.
- Filtering drinking water for fluoride and reducing brominated flour and flame-retardant exposure supports thyroid health.
Key Moments
Why TSH alone misses 98 percent of thyroid problems
McCall McPherson explains that TSH and even T4 together reflect only one to two percent of variation in the active hormone T3, meaning standard lab panels miss nearly all thyroid dysfunction. For longevity, TSH should be around one or slightly under.
"Research shows TSH and even, if someone's checking your TSH and your T4, it reflects variation in your T3 in one to two percent at the time."
Fluoride, bromine, and environmental thyroid suppressors
The episode reveals how everyday environmental exposures like fluoride in tap water and toothpaste, bromine in wheat products, and common medications directly suppress thyroid function, contributing to the epidemic of undiagnosed thyroid disorders.
"Directly suppresses function and they put it in water and we've known this since 1945 and you're drinking tap water and you're brushing with fluoride toothpaste and then you're eating wheat that's treated with bromine, you're taking a stack of drugs."
Treatment-resistant depression may actually be untreated thyroid dysfunction
McCall McPherson describes how treatment-resistant depression is frequently thyroid dysfunction in disguise, citing research showing that patients do not improve until TSH drops below two, which is far lower than standard medical cutoffs.
"Treatment-resistant depression was my entry point with patients, for sure."
