In an attempt to establish the diagnostic value of serum triiodothyronine and to correlate it with pathophysiologic mechanisms of thyroid hormones in various thyroid disorders, the author measured the serum triiodothyronine levels by means of radioimmunoassay and compared them with other thyroid function tests.
This study was carried out in 152 oases- with various thyroid functions; 28 cases as control, 51 cases of hyperthyroidism, 50 cases of euthyroidism and 23 cases of hypothyroidism. The results obtained were as follows:
1. The serum T3 level in normal control group ranged between 131±34 ng/dl.
2. The serum T3 levels ranged between 306±97 ng/dl in hyperthyroidism 138±32 ng/dl in euthyroidism and 60±27 ng/dl in hypothyroidism. The significant differences between these groups were noted in this study.
3. In 5(9.9%) out of 51 cases with hyperthyoidism and 9(39. 1%) of 23 cases with hypothyroi disco, the serum T3 were measured to be in normal range. Accordingly, the diagnostic value of the measurement of serum T3 with hyperthyroidism was justifiable, but with hypothyroidism, itt was less creditable than that of serum thyrotropin.
4. There was little significant difference between the diagnostic value of serum thyroxine and triiodthy ronine levels in various thyroid disorders. However, T4/T3 ratio was decreased in patients with untreated hyperthyroidism because of more elevation of T3 than Ti. Consequently, the serum T3 was more sensitive than Ti in some thyroid disorders.
The serum T3 level was much more sensitive and showed prompt shift in its level during the course of treatment on the patient with various thyroid disorders. And the measurement of serum T3 was a good index for the evaluation of the thyroid function.
From these results obtained, the measurement of serum T3 by means of radioimmunoassay is a good way to understand the status of thyroid function with various thyroid disorders and evaluate the effects of the treatment given on these patients.
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