[Triiodothyroacetic acid in euthyroid goiter. New data on its mechanisms of action. Comparison with L-thyroxin].

Euthyroid goiter is usually treated with THS-inhibiting doses of L-thyroxin (L-T4), which can have troublesome adverse effects. It has been suggested that triiodothyroacetic acid (Triac), a TSH suppressor, might have fewer peripheral effects and better tolerability than T4. We therefore compared the risk-benefit ratios of the two drugs. Thirty-six women with euthyroid goiter (no thyroid cancer) were randomized to receive either Triac (19.6 ug/kg) (n=19) or L-T4 (1.7 ug/kg) (n=17) for 11 months. Goiter volume, lumar and femoral bone mineral density, and serum osteocalcin, deoxypyridinoline, TSH, free T4, and total cholesterol, high-density cholesterol (HDL), low-density cholesterol (LDL), and triglycerides were determined before and after treatment. Student's test and X2 analysis were used. TSH values (microunits/ml) in the Triac and T4 groups were respectively 1.91 +/- 0.6 (basal) and 0.18 +/- 01 (after) and 2.1 +/- 2.5 (basal) and 0.18 +/- 0.3 (after). Thyroid volume fell by 37.9 +/- 35.4% in the Triac group and by 14.5 +/- 39.5% in the L-T4 group (p=0.069). Goiter volume fell by at least 50% in 42% of patients treated with Triac and in 17.7% of patients treated with L-T4 (p=0.15). Triac was associated with fewer adverse events. Changes in bone mineral density, serum deoxypyridinoline, serum osteocalcin and the lipid profile did not differ between the treatment arms. However, the Apo B level fell more strongly on Triac than on T4. These results show that Triac is more effective than L-T4 on goiter size, while having similar peripheral effects.