Thyroid nodules are a very common issue in the adult population. Thyroid scintigraphy is the only method available to assess the functional characteristics of thyroid nodules. Hyperfunctional nodules, also known as hot or autonomous nodules, are characterized by an increased isotope uptake compared to the adjacent thyroid parenchyma. They present activating somatic mutations in the TSHR and GNAS genes, are rarely malignant, and their prevalence increases in iodine-deficient regions. Cytological examination of these nodules frequently shows indeterminate results, which can lead to unnecessary therapeutic procedures.
Although recommendations limit scintigraphy use to thyroid nodule assessment in cases of low serum TSH, many European studies have shown that a subnormal TSH level does not effectively exclude the presence of a hyperfunctional nodule. In our prospective study conducted between 2018 and 2021, among the 67 hyperfunctional nodules evaluated, 50% of patients presented with normal serum TSH levels, 70% had a EU-TIRADS 4 ultrasound score suggesting an intermediate malignancy risk, and 50% of the nodules submitted to cytology yielded indeterminate results. No malignancy was detected upon histological examination of the hyperfunctional nodules submitted to surgical excision.
Scintigraphy may still be relevant in the initial assessment of thyroid nodules in selected populations, namely patients with a TSH level <2mU/L in regions with past or current iodine deficiency, in order to avoid unnecessary diagnostic and surgical procedures.
Keywords
Autonomously hyperfunctioning nodules, scintigraphy, indeterminate cytology, thyroid cancer, EU-TIRADS