Simple nodular goiter is a common disease and the effectiveness of levothyroxine suppressive therapy in reducing nodule size remains controversial. In this study, we evaluated the effect of levothyroxine administration on thyroid nodule volume and thyroglobulin levels. Twenty-two patients with palpable solitary thyroid nodules were given 75-150 mg/day levothyroxine treatment in low and high dose suppression groups for six months and ten patients were given placebo. High-resolution (7.5 MHz) ultrasonography was used to measure the volume of nodules before and after levothyroxine therapy. Serum TSH levels were significantly suppressed in both treatment groups, being more prominent in the high dose group. Mean nodule volume in the high dose group decreased significantly from 1.91 ± 1.51 ml to 1.19 ± 1.25 ml (p<0.05). In the low dose group the reduction of mean nodule volume was also significant (2.61±2.26 ml vs 1.94±2.04, p<0.05). Serum thyroglobulin levels decreased in both groups [92.3 ± 100.1 mg/l vs 40.8 ± 53.2 mg/l (p<0.05) in the high dose group; and 86.4 ± 101.8 mg/l vs 55.7 ± 78.7 mg/l (p<0.05) in the low dose group. Thyroglobulin concentrations did not change significantly (66.5 ± 83.7 mg/l vs 62.7 ± 69.9 mg/l) in the control group. There was a correlation between pretreatment thyroglobulin levels and nodule volume (r=0.64, p=0.0001) and this correlation persisted following treatment (r=0.66, p<0.0001). We conclude that both low and high dose levothyroxine therapy is effective in the treatment of thyroid nodules and follow up of thyroglobulin levels may be used as a predictor of treatment response.
Keywords: Levothyroxine, suppressive treatment, thyroid nodules and thyroglobulin