| A Lab’s Normal TSH, T4, T3 Levels May be Abnormal for You | |
March 2002 -- Danish researchers conducted an interesting study, looking at the monthly thyroid levels -- T4, T3, free T4 index, and TSH -- of 16 healthy men with over a period of 12 months. What they found was that each of the individuals had different variations of their thyroid function, around unique levels - or “set points.”
Each person had his own individual thyroid function and normal level, and people tended to fluctute slightly within their own range.These findings led the researchers to conclude that a thyroid test result within a laboratory’s reference limits - or “normal range” -- is not necessarily normal for a particular individual. In fact, the researchers also concluded that the distinction between subclinical and overt thyroid disease (abnormal serum TSH and abnormal T4 and/or T3) is somewhat arbitrary, because the patient’s normal set point for T4 and T3 within the laboratory reference range is actually illustrative and needs to be taken into account.
Reference: “Narrow Individual Variations in Serum T4 and T3 in Normal Subjects: A Clue to the Understanding of Subclinical Thyroid Disease,” The Journal of Clinical Endocrinology & Metabolism, Vol. 87, No. 3 1068-1072, 2002.
