Abstract
Thyroid scintigraphy is now rarely used in the work-up of a thyroid nodule except in the presence of a low TSH value. Therefore, autonomously functioning thyroid nodules (AFTNs) with a normal TSH value are diagnosed only in the rare medical centers that continue to use thyroid scan systematically in the presence of a thyroid nodule. In this review, we discuss the prevalence of AFTN with a normal TSH level and the possible consequences of performing fine needle aspiration cytology (FNAC) in an undiagnosed AFTN. We also discuss the risk of malignant AFTN which may be higher than previously stated.
Highlights
Thyroid nodules are a very common problem in adults
This strategy is based on the assumption that autonomously functioning thyroid nodules (AFTNs) are uncommon and that thyroid-stimulating hormone (TSH) levels are always subnormal in the presence of an AFTN and that a normal TSH value rules out the presence of an AFTN
We address the following points: 1. Does normal TSH exclude a hyperfunctioning thyroid nodule? The American Thyroid Association (ATA) and the European Thyroid Association (ETA) guidelines recommend considering radionuclide scanning in patients with thyroid nodules only if the TSH level is low[3,17]
Summary
Thyroid nodules are a very common problem in adults. Their prevalence increases with age and may reach 50% by the age of 65 years[1,2]. In the absence of thyroid scintigraphy in the workup of a patient with a thyroid nodule and a normal TSH level, there is a risk of performing FNAC in an unsuspected AFTN. We cannot claim that this observation is valid for patients from areas with sufficient iodine intake Another limitation of these studies is the fact that thyroid scans were generally performed using 99mTcO4- rather than 123I and that some nodules may appear “hot” on 99mTcO4- but are cold on 123I. Iodide perchlorate test was used to evaluate organification defect in patients with an autonomously functioning thyroid nodule (AFTN). The most advanced multigene molecular panels provide both high positive predictive value and high negative predictive value for cancer detection in thyroid nodules, and in the near future they will probably eliminate indeterminate cytologic diagnosis of thyroid nodules These techniques have never been studied for suspicious cytology obtained in an AFTN. The huge variation of the risk of malignancy within AFTNs between the different studies reported in Mirfakhraee et al.’s review (between 0% and 12.5%) raises the question of potential bias and underlines the need for prospective studies[38]
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