Effect of triiodothyronine on the serum lipids and lipoproteins of euthyroid and hyperthyroid subjects.

Abstract

l-Triiodothyronine (0.4 to 6.0 mg. daily) was administered in fractional doses intravenously for three to twenty-three days to 3 euthyroid subjects, 1 hyperthyroid patient during a partial spontaneous remission, and 1 patient with severe thyrotoxicosis. Hypermetabolism was produced in the euthyroid subjects and increased in the hyperthyroid patients. Serum lipid and lipoprotein levels began to decrease within one to four days after the beginning of triiodothyronine therapy. The decrease in total lipid varied from 15 to 50 per cent, in lipid phosphorus from 19 to 56 per cent, and in total cholesterol from 23 to 56 per cent. Changes in protein fractions were inconstant. The serum lipid values returned to the control levels within seven to fifteen days after triiodothyronine was omitted. The observed fall in lipid values persisted after cessation of therapy longer than did the other clinical and laboratory evidences of hypermetabolism, which subsided within four to sixdays