Free T3 thyroid hormone (FT3)
Free T3 is the most active thyroid hormone and is primarily produced from the conversion of T4 in peripheral tissue. Approximately one third of T4 is converted to T3.

Specialists see better results when T3 is in the upper 25th percentile of the normal range. The normal range is, however, applicable when prescribing T4, which is converted to T3 in the cell and then the amount that leaks back into the serum is the “normal” level. When treating with T3, this is not the case so standard reference ranges cannot be used. Mental and environmental stressors can inhibit the conversion of T4 to T3, thus decreasing the amount of active thyroid hormone available to the cells.

Serum (Blood Draw) or Blood Spot

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