Thyroid Metabolism After T4 Is Present & TSH Is Normal

The reason that you can still have symptoms is that T4 is relatively weak metabolically. That means that it doesn’t have much impact upon physiology. T4 needs to be converted into T3. T3 and NOT T4 is the active form of thyroid hormone. T3 has to be absorbed into cells in order to become active. Abnormalities in the conversion of T4 into T3 and the uptake of T3 by individual cells throughout the body can be caused by over 20 factors that have nothing to do with TSH. Over-reliance upon TSH as the marker to assess thyroid metabolism misses the overwhelming majority of ways thyroid metabolism can be disrupted and leads to millions of people suffering.