Ten U.S.P. of TSH (Thytropar) was administered intramuscularly for three days to five euthyroid controls, to thirteen patients with chronic thyroiditis (four clinically euthyroid patients with normal serum TSH-Group I, five clinically euthyroid patients with high serum TSH-Group II, four clinically hypothyroid patients with high serum TSH-Group III), and to five patients with thyroidal hypothyroidism.
Thyroidal 24hr uptake of
131I, 24hr urinary T
3 and serum T
3 levels were measured.
In the euthyroid controls, the basal urinary T
3 value was 0.76±0.26 (mean±S.D.) pg/day and increased to 1.31±0.16 on the first day, to 2.33±0.75μg/day on the second day, and to a maximum of 2.78±0.65μg/day on the third day after the TSH administration.
In Group I, basal urinary T
3 was normal at 0.58±0.16μg/day. Following the TSH administration, the value increased to a maximum of 1.60±0.62/μg/day, but the increase rate was less than that in the euthyroid controls. In Group II, basal urinary T
3 was normal at 0.71±0.37μg/day. Following the TSH administration, however, this value did not increase. In Group III, basal urinary T
3 was significantly low at 0.32±0.07μg/day, and this value did not increase after the TSH administration.
In the thyroidal hypothyroid patients, basal urinary T
3 was 0.12±0.10μg/day and lower than that of Group III, and it did not increase after the TSH administration.
Positive correlations were found between urinary T
3 and serum T
3 before and after the TSH administration.
In contrast to basal serum T
3 and urinary T
3, the mean basal thyroidal uptake of
131I in patients with chronic thyroiditis was higher than that of the euthyroid controls. However a positive correlation was found between the increase rate of urinary T
3 and that of the thyroidal uptake of 131 I after TSH administration.
These observations indicate that the changes in concentration of urinary T
3 are reliable indices of thyroidal response to TSH administration in various states of thyroid function.
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