Distinguishing Diagnostic and Treatment TSH
A Narrower Normal Values Range for Treating Hypothyroidism
Sep 27, 2009
The goal of thyroid hormone therapy to treat patients with hypothyroid conditions is to suppress their elevated TSH levels, down to a lower normal level. Keeping TSH at a higher normal level, even if that level remains within normal values, may not result in adequate treatment for some patients.
Diagnostic TSH Range
The normal values TSH range for detecting thyroid hormone imbalance at medical blood labs has a high-normal boundary and a low-normal boundary. Readings falling outside of those, even slightly, can indicate an existing thyroid hormone imbalance or one that is developing. The range will be fairly wide, so that less-than borderline cases do not appear to be abnormal readings, which can be misleading to a doctor, resulting in additional testing or follow-up monitoring that may not be necessary.
A blood lab for example may have a normal range for TSH, to diagnose thyroid dysfunction that is from 0.4 to 4.0 and readings that fall below 0.4 indicating thyroid hormone levels are elevating in the body and readings rising above 4.0 indicating thyroid hormones are decreasing in the body. If readings are at either of the cut-off levels but not outside of them (borderline), these cases still merit follow up retesting because they may point to developing thyroid hormone imbalance. This is a fact stated by the U.S. National Institutes of Health.
Treatment TSH Range
When hypothyroidism is being treated, which can develop directly from a disease process or following treatment for hyperthyroidism, the goal is not simply to correct the TSH level back into the normal values range. The goal is rather to treat the hypothyroidism, so that TSH is at a level that also places the thyroid hormones (T4 and T3) at the proper level to relieve symptoms of hypothyroidism and to correct the patient’s slow functioning metabolism. A borderline high or higher-normal TSH level may not accomplish this, in fact some patients may require TSH to be suppressed to low-normal levels to properly increase the T4 and T3. Blood testing all three levels together can better help to determine where the TSH level needs to be.
Diagnostic TSH Range may be Too Wide at Some Labs
Both the AACE (American Association of Clinical Endocrinologists) and the NACB (National Academy of Clinical Biochemistry) have recommended that labs with wide TSH ranges, narrow those ranges to a level that detects more cases of developing thyroid hormone disorders. The AACE has expressed belief that TSH levels above “3.0” may indicate developing hypothyroidism, while the NACB states that the upper limit (high normal) TSH reference range may at some point need to be reduced to “2.5”. This based on their observance of fact that 95% of euthyroid (normal thyroid function) individuals test between “0.4 and 2.5”.
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