McCall McPhersonFounder, Modern Thyroid Clinic.

Thyroid Hormones: T4 Risks vs. T3 Benefits! #shorts

14 Oct 2026 · 2 min

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1:42

In this YouTube short, McCall McPherson critiques the conventional reliance on TSH and highlights recent research comparing thyroid hormone levels. He explains that low free T3—common among "poor converters" and patients on levothyroxine—correlates with a 1.8‑fold increase in dementia risk and higher incidences of diabetes and heart disease. Conversely, higher free T4 is linked to greater overall mortality, more osteoporosis/osteopenia, and the same chronic diseases. In contrast, high‑normal free T3 is associated with lower mortality, fewer cardiovascular events, reduced bone loss, higher socioeconomic status, more work hours, later retirement, and lower disability risk. McPherson argues that because TSH showed no association with these outcomes, using TSH as the primary thyroid marker misguides clinical decisions.

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was associated with higher levels of dementia, diabetes, heart disease. Dementia, 1.8 times higher, specifically associated with low T3, not even subclinical hypothyroid. I just mean every normal person out there walking around in America that is a poor converter has a 1.8 times higher risk of developing dementia. Again, think poor converters, think people on levothyroxine, Synthroid, Unithroid, Levoxyl, Tirosint versus higher levels of T3 and looked at health ramifications of both. Let me remind you, in medicine, we are taught high levels of free T3 or giving your patients free T3 will cause osteoporosis, heart attack, stroke, high blood pressure, a slew of health problems. What this study showed is higher levels of T4 is associated with higher levels of mortality. It was associated with higher incidence of osteoporosis, osteopenia, It was associated with higher levels of dementia, diabetes, heart disease. We're talking about high normal levels of T3 was associated with lower risk of mortality, lower risk of heart disease, cardiovascular events, osteoporosis, osteopenia, higher socioeconomic status, more hours worked, later retirement, and reduced risk of disability. It's like I just hit the absolutely hit the thyroid. Jackpot with that one. TSH had no link to any of these things. So when we are relying again on TSH to be the marker, the inference for all of this other data, we're going down the wrong path. We're barking up the wrong tree.