Natural course of benign thyroid nodules in a moderately iodine-deficient area

Few studies using ultrasonographic evaluation have addressed the natural course of benign thyroid nodules. In this study, we present the long-term analysis of benign, untreated thyroid nodules in a moderately iodine-deficient area.

We collected the retrospective data for 531 nodules in 420 patients followed by ultrasonography for a mean time period of 39.7 +/- 27.8 months (range 12-168 months).

When we considered significant nodule size decrease criteria as decreases in nodule volume of at least 15% and 30%, we found that 33.1% and 20.7% of thyroid nodules decreased in size, respectively. Using the criteria of a greater than 15% and 30% increase in volume showed that 32% and 24.1% increased in size, respectively. A logistic regression analysis using mixed models to predict thyroid nodule growth (volume change > or = 15%), including age, TSH, sex and time between evaluations, failed to predict nodule growth. Only hypoechoic echo pattern remained as a statistically significant predictor of growth.

In 40 months' follow-up, we found that benign thyroid nodules exhibited a mostly favourable clinical natural course. One-third of benign thyroid nodules showed continuous growth, one-third remained unchanged, and the other third decreased in size.