De novo Lesions Frequently Develop in Adult Normal Thyroid Over Almost Six Years

Purpose: In order to understand how thyroid abnormalities emerge over time in adults,
we evaluated incidence of thyroid diseases in healthy subjects, after almost 6 years from
a previous negative ultrasound.
Methods: Anamnestic and physical data were collected. Ultrasound neck evaluation
was performed by an experienced endocrinologist, recording detailed thyroid and
nodules characteristics. Nodules were classified according to American Thyroid
Association classification for prediction of cancer risk. Serum samples were collected for
subsequent evaluations (TSH, free thyroid hormones, calcitonin, anti-thyroid antibodies).
Anamnestic, clinical, sonographic, and serological characteristics were analyzed with
logistic regression analysis for subjects with nodules vs. those without.
Results: One hundred and eleven subjects were enrolled (43M, 68F). Half of them
developed nodules, mainly smaller than 1 cm and without suspicious characteristics.
Ninety-seven percent were euthyroid. Only 4% had serological diagnosis of thyroiditis.
Incidence of thyroid diseases was higher in women, especially nulliparous. Comparing
clinical characteristics of subjects with and without nodules, the only statistically
significant difference concerned thyroid volume adjusted for body weight or surface
(p < 0.05), but not residual volume excluding nodules. Multivariate logistic regression
analysis showed that female gender, higher BMI-adjusted thyroid volume and residual
thyroid volume excluding nodules, nulliparity, age, and fT3 increase the risk of
developing nodules.
Conclusions: These results demonstrate that adult thyroid tissue undergoes changes
that are already detectable by US after almost 6 years. Half of the enrolled subjects
developed de novo nodules or colloid cysts of poor clinical relevance.