MATERIALS AND METHODS
Patients from the obesity and diabetes clinics of two Endocrinology Units (Hospital General de Granollers and Hospital de Mollet), older than 18 years and with obesity, defined as a body mass index (BMI) ≥ 30 kg/m2, were asked to participate.
After signing the informed consent, patients were examined clinically and a thyroid US and the determination of serum anti-thyroperoxidase antibodies (TPOAb) and TSH levels were planned.
Exclusion criteria were the inability to understand the study, the presence of personality traits in which the practice of thyroid US and the possible detection of nodular pathology could generate an undue anxiety, and the presence of previously other known autoimmune diseases, thyroid nodules or thyroid cancer. Specifically, patients with obesity who consulted for suspected functional or nodular thyroid disease were not included in the present study.
Thyroid US were performed and interpreted by experienced endocrinologists using an Esaote Mylab9 scanner (Hospital de Granollers) or a Siemens Sonoline G40 scanner (Hospital de Mollet) both equipped with a high-resolution linear transducer (7.5–14 MHz).
Serum TPOAb were measured in an Immulite 2000 XPi Immunoassay System (Siemens Healthcare GmbH, Erlangen Germany) and expressed as IU/ml. Normal values for TPOAb were <35 IU/ml. Serum TSH was measured in a Cobas e170 analyser (Roche Diagnostics LTd, Rotkreuz, Switzerland; normal values 0.3-4.2 μIU/ml).
Patients were classified according to neck palpation (i.e. abnormal vs. normal) and the presence of the pre-specified risk factors, i.e. family history of thyroid cancer, radiation exposure, Hashimoto’s thyroiditis and elevated TSH or treated hypothyroidism. Patients were considered as harbouring Hashimoto’s thyroiditis if TPOAb levels were higher than the upper limit of reference. Likewise, TSH levels were considered high if they exceeded the upper normal reference value.
Thyroid nodules detected by thyroid US were classified as specified by the current guidelines of the American Thyroid Association (ATA) [16] and fine needle aspiration biopsy (FNAB) was indicated accordingly, with the exception of subcentimeter nodules with a high suspicion echographic pattern where FNAB was also considered. FNABs were performed and processed using standard protocols [17] and were evaluated by the Department of Pathology of Hospital de Granollers using the Bethesda reporting system [18]. Surgical treatment was planned according to current guidelines [16]. In a post-hoc analysis nodules were classified following the TI-RADS classification of the American College of Radiology (ACR) [19].
Follow-up of nodules not subjected to surgery and of those without indication of FNAB was performed at discretion of the attending physician.
Data are presented as number (n) and standard deviation (SD) or percentages with 95% confidence intervals (CI) when appropriate. The differences in the frequency of thyroid nodules between groups were analysed with Pearson’s Chi-squared test at a significance level of p<0.05. To test for differences between the present results and those previously hypothesized we used inference statistics for one sample using as reference the proportions stated by Cham et al [15]. Analyses were performed using free online statistical packages (https://www.socscistatistics.com and https://www.medcalc.org/calc/test_one_proportion.php).
The study was approved by the research committees of the participating centres. No specific funding was received for the development of the study.