Thirty-five years ago, Broda Barnes, M.D. Endocronologist, wrote a book titled, "The Riddle of Heart Disease Solved." His hypothesis was low thyroid leads to increased cholesterol, artery damage, heart weakness, weight gain, poor metabolism, fatigue, and heart disease. Thirty-five years ago, there was no useful test for thyroid function. Dr. Barnes relied on body temperatures, reflex testing, and observation of the patient. He advocated the use of natural thyroid from pig thyroid glands.

Over the years, lab testing was developed to test for T4 (thyroxine hormone) and TSH (thyroid stimulating hormone). Many people who were doing well on Thyroid were taken off medication because of normal T4 and TSH.

Fifteen years ago, a new test was developed that could detect the very small amount of T3 (triiodothydoxine) that was not bound to protein. Free T3 is the only part of the
thyroid hormone that regulates the metabolism of the cells. The amount of T3 and TSH do not reflect the status of Free T3. T4 must convert to T3, T3 can be bound to protein or be unbound.

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Free T3 decreases with age and disease. The T4 does not reduce significantly with age or disease. Free T3 is the bottom line in thyroid function. A recent study published in the journal “Circulation” states that low levels of Free T3 were associated with increased number of heart deaths. Thyroid function tests by Free T3 is the most predictable factor in who will die from their heart.

The Mayo Clinic recently coined the term “Low Free T3 Syndrome” to separate the hypothyroid (Low Free T4, High TSH) from Low Free T3.

We began using Free T3 testing fifteen years ago. After testing several thousand patients for Free T3, I am convinced this is the single most important test we perform.

The two standard deviation range of Free T3 is 230–420. Only 2½% below 230 or above
420. We like to have our patients’ levels in the top 25%, or 365 to 420. This means most of our patients (80%) need to take some natural thyroid supplementation.