We prospectively evaluated the effect of thyrotropin (TSH)-suppressive therapy with levothyroxine (LT4) on the size of a benign, solitary, solid nodule and multinodular goiter in a relatively low iodine intake area. In this study, 101 euthyroid subjects with a benign, solitary, predominantly solid nodule (n = 54) confirmed by biopsy or multinodular goiter (n = 47) received 200 microg of levothyroxine daily as a single morning tablet for 12 months. Thirty-five receiving no therapy were considered as controls (solitary nodules, n = 20, multinodular, n = 15). Patients were admitted to the study after evaluation of thyroid biochemical parameters (thyroxine [T4], free thyroxine [FT4], triiodothyronine [T3], thyrotropin [TSH], and thyroglobulin [Tg]), thyroid scanning, ultrasound examination, and fine-needle aspiration biopsy. Every 3 months, thyroid function tests and every 6 months ultrasound examinations were repeated. Twelve months later 20 of 54 (37.1%) patients with single, solid nodules had 50% or more regression of the nodular volume (responders). Eleven of 54 (20.3%) patients had more than 20%, but less than 49.9% reduction of nodular volume (partial responders). Nonresponders were 23 of 54 (42.5%). One-third of subjects with multinodular goiter had 50% or more regression of the glandular volume, whereas 46.8% were considered as nonresponsive. The mean serum Tg levels decreased significantly only in responders with solitary nodular disease or multinodular goiter. In the control group only 1 patient (5% of total) with a solitary nodule had a 50% reduction in the nodular volume. Five others had a partial response (<49%, >20% reduction). None of the patients with multinodular goiter had a significant reduction (>50%) of the combined nodular volumes. We concluded that LT4 may be effective, among other factors, in arresting the growth or in reducing the volume of relatively small, benign, solitary, solid thyroid nodules or the combined nodular volume of multinodular goiter.
