“Your TSH is Normal”
British Medical Journal 326:311-2
Serum TSH in assessment of severity of tissue hypothyroidism in patients with overt primary thyroid failure: cross sectional survey
Meier C, Trittibach P, Guglielmetti M, Staub JJ, Muller B.
In 49 patients with primary hypothyroidism, the authors investigated the correlation of TSH, free T4 and T3 with the level of tissue hypothyroidism (thyroid effect in the body) and found a very poor correlation of TSH with tissue levels of thyroid. They found there was a better correlation with free T4 and T3.
This study demonstrates that standard thyroid tests do not correlate with tissue levels of thyroid and serves as more evidence that standard thyroid tests cannot be relied upon to correctly determine the thyroid status of an individual. Most physicians and endocrinologists incorrectly feel the TSH is the best indicator of the thyroid status of an individual and do not understand that the TSH is a poor indicator of tissue thyroid levels in many people. They fail to understand that a person may suffer from significantly low thyroid despite having a normal TSH, free T3 and free T4. The authors discuss the need for doctors to look at signs and symptoms to determine optimal levels of thyroid replacement and not rely on the TSH, which is rarely done by physicians and endocrinologists.
The authors summarize, “TSH is a poor measure for estimating the clinical and metabolic severity of primary overt thyroid failure… In contrast to the good correlations with both circulating thyroid hormones, we found no correlation or only weak correlations with serum TSH… We found no correlations between the different parameters of target tissues and serum TSH…Therefore, the biological effects of thyroid hormones at the peripheral tissues—and not TSH concentrations—reflect the clinical severity of hypothyroidism. A judicious initiation of thyroxine treatment should be guided by clinical and metabolic presentation and thyroid hormone concentrations (free thyroxine) and not by serum TSH concentrations.”