Abstract
The various types of ”Triiodothyronine (T3) Suppression Test” were performed on 576 patients (160 with ”Nontoxic Diffuse Goiterh, 205 with”Toxic Diffuse Goiter” and 221 with ”Treated Hyperthyroidismh which consisted of 86 clearly euthyroid, 41 quesionable, 76 clearly hyperthyroid and 8 hypothyroid state).
T3 was administered orally at a dose of 50 μg. or 100 μg daily. Thyroidal I131-uptake at 24 hours was evaluated before and on the 3rd, 6th, or 13th day during T3 administration. The effect of each type of T4 administration on thyroidal I-131uptake is expressed as the suppressibility which was calculated by the following formula :
S (%) =U1-U2/U1×100
S : suppressibility
U1 : thyroidal I131 uptake before T3 administration
U2 : thyroidal I131 uptake during T4 administration
1) In the patients with ”Nontoxic Diffuse Goiter”, the mean value of suppressibility was 65.1 % on the 6th day during T4 administration of 50 μg/day, 48.6% on the 3rd day, 74.0% on the 6th day and 91.4% on the 13th day during T3 daministration of 100 μg/day, respectively, with the lower limit of normal suppressibility, which was calculated as lower rejection limit of suppressibility, of 15.9% on the 6th day during T3 administration of 50μg /day, -9.0% on the 3rd day, 35.9% on the 6th day and 73.5% on the 13th day during T3 administration of 100μg./day which incresed in accordance with an increase of either daily doses or duration of T3 administration.
2) In the patients with”Toxic Diffuse Goiter”, the mean value of suppressibility in each type of T3 administration was-3.9% on the 6th day during T3 administration of 50 μg/day, -16.8% on the 3rd day, 0.3% on the 6th day and 4.0% on the 13th day during T3 administration of 100/2g./day, respectively, showing low value. In some cases, however, the normal suppressibility was obtained in each group, e.p. 11.1% on the 6th day during T3 administration of 50 μg. /day, 60.0% on the 3rd day, and 0.9%, on the 6th day during T3 administration of 100 μg./day, but none on the 13th day during T3 administration 100 μg./day.
3) In ”Treated Hyperthyroid” patients who were in the clearly euthyroid state, 66.7% of them on the 6th day during T3 administration of 50 μg. /day 80.0% of them on the 3rd day, 45.4% on the 6th day and 16.0% on the 13th day during T, administration of 100 μg./day revealed the normal suppressibility. There were however, some cases which revealed the normal suppressibility in the patients who were still clearly in the hyperthyroid state, e.p. 27.3% of them on the 6th day during T3 administration of 50 μg./day, 100% of them in the 3rd day and 2.0% of them on the 6th day during T3 administration of 100 iig/.day, but none on the 13th day during T3adminstration of 100 μg. /day. On the 6th day during T3 administration of 50 μg. /day and on the 6th day during that of 100 μg/day, a case revealed the normal suppressibility only 4 months after the treatment for hyperthy-roidism while there were no cases which revealed the normal suppressibility within 5 years after treatment for hyperthyroidism on the 13th day during T3 administration of 100 μg./ day.
It seems that the “Triiodothyronine Suppression Test” by giving T3100 μg./day orally for 14 days is more reliable index of evaluation for the relationship between the hypophysis and thyroid gland than by any other type of T3 administration employed in this experiment.
