A prospective randomized trial of levothyroxine suppressive therapy for solitary thyroid nodules.

Objective: We examined the effects of L-thyroxine therapy versus placebo over a 12-month period on volume of solitary thyroid nodules.

Design: Prospective randomized clinical trial; placebo and control groups followed for one year in three centres.

Patients: One hundred and one euthyroid patients with single palpable colloid thyroid nodules.

Measurements: Serum thyroid hormones, TSH, thyroglobulin, anti-thyroglobulin and anti-thyroid peroxidase antibodies measured at the first visit and after 2, 6 and 12 months; nodule volume and contralateral thyroid lobe thickness measured by ultrasound in double blind fashion; nodule diameter measured by palpation every 6 months.

Results: In the treatment group the nodule volume measured by ultrasound decreased progressively but not significantly; in the placebo group no changes were demonstrated. The number of nodules which decreased in size was however significantly larger in the treatment group. None of the initial parameters was predictive for the response. In the treatment group the nodule size assessed by palpation showed a significant decrease after 12 months when compared to baseline.

Conclusions: In non-endemic areas TSH suppression induces nodule volume reduction measured by ultrasound which, although not significant, seems to be progressive and occurring only in a subgroup of patients. Significant palpatory nodule reduction is probably related to decreased thickness of the surrounding thyroid tissue still responsive to TSH.