THE EFFECT OF TREATMENT WITH LEVOTHYROXINE OR IODINE ON THYROID SIZE AND THYROID GROWTH-STIMULATING IMMUNOGLOBULINS IN ENDEMIC GOITER PATIENTS

OBJECTIVE We assessed the effect of levothyroxine or iodine on thyroid size and on thyroid growth stimulating immunoglobulins in endemic goi tre patients. DESIGN Levothyroxine or iodine was given orally in an op en randomized prospective study (100 and 200 mug respectively). PATIEN TS Thirty-seven euthyroid patients with diffuse iodine deficiency goit res and thyroid growth stimulating immunoglobulins were studied. MEASU REMENTS Thyroid size, thyroid growth stimulating immunoglobulins (mito sis arrest assay), basal TSH, free T3, free T4, thyroid anti-microsoma l antibodies, antithyroglobulin antibodies, anti-TSH receptor antibodi es and urinary iodine excretion were measured. RESULTS Thyroid size de creased significantly in both groups, in the levothyroxine group more than in the iodine treated group. Thyroid growth stimulating immunoglo bulins levels also decreased significantly in both groups. Between gro ups there was no statistically significant difference. A statistically significant correlation between thyroid growth stimulating immunoglob ulins reduction profiles and goitre size reduction could not be establ ished. TSH levels became suppressed in the levothyroxine group while t he T4 values rose; in the iodine treated group TSH levels stayed const ant as did T4. None of the patients developed thyroid microsomal or th yroglobulin autoantibodies and/or hyperthyroidism during the treatment . CONCLUSIONS Levothyroxine as well as iodine was effective in reducin g thyroid size as well asthyroid growth stimulating immunoglobulins le vels in endemic goitre patients. Since in both groups TSH levels were not related to thyroid size reduction, other factors than TSH suppress ion must be responsible for the observed thyroid size reduction. Iodin e itself by virtue of its antiproliferative action on thyrocytes may h ave had a direct action on the goitre reduction during iodine treatmen t; however, the levothyroxine dose, containing less iodine, had a simi lar effect. A complicated picture hence emerges with regard to factors involved in the shrinkage of iodine deficiency goitre during thyroxin e or iodine therapy. These findings indicate that TSH and thyroid grow th promoting immunoglobulins are not the only influences on the size o f endemic goitres, although it cannot be excluded that these two facto rs contribute to influence the pathogenetic process.