Changes in thyroid nodule volume caused by fine-needle aspiration: a factor complicating the interpretation of the effect of thyrotropin suppression on nodule size.

The effectiveness of TSH suppression therapy for thyroid nodules remains controversial. Prior studies have assumed that the fine-needle aspiration biopsy (FNAB), used to confirm a benign condition before the establishment of control and treatment groups, has no effect on nodule volume. Seventeen untreated euthyroid patients with clinical solitary thyroid nodules that were solid (on high-resolution ultrasound) and a colloid goiter (on cytologic examination) had ultrasound measurements of nodule volume before a FNAB, immediately thereafter, and 1 month and 6 months later. Size differences and individual variability at each time period were analyzed. No significant difference in mean thyroid nodule volume was present at any point after the FNAB; however, the changes in nodule volume were quite marked and bidirectional among patients masking the cumulative effect. The variability of the change in individual nodule volume was statistically significant when comparisons were made across time (P = 0.0032). FNAB of thyroid nodules results in significant individual changes in volume after the procedure. Studies, such as the effect of TSH suppression on thyroid nodule volume, that incorporate the FNAB in both control and treatment arms of the experimental design, need to take these changes into account, less erroneous conclusions result.