TSH levels are associated with increased risk of thyroid carcinoma in patients with nodular disease

Several studies have shown an increased risk of thyroid malignancies in patients with elevated TSH levels, even if these levels fell within the normal range. The aim of this study was to evaluate the relationship between TSH and risk of malignancy in patients with thyroid nodules. We included 622 patients with thyroid nodules evaluated by fine needle aspiration and/or thyroidectomy and diagnosed by cytology or histology. Clinical and laboratory data, such as gender, weight, ultrasound findings, serum TSH, and free T4, were obtained from medical records or collected during each patient's first visit to our centre, prior to any intervention. Thyroid cancer was more prevalent in males (p = 0.012) and in patients with a solitary nodule (p < 0.01). Malignant tumours were predominantly solid, whereas benign tumours were solid or mixed (p = 0.053). The carcinoma risk in patients with thyroid nodules increased with increasing serum TSH concentration, with a significant elevation in patients with serum TSH levels above 1.64 mU/L (p < 0.001). This relationship persisted even when the subgroup of patients undergoing thyroidectomy was analysed separately. Patients with follicular lesions presented with significantly higher TSH levels compared to patients with benign cytology (p < 0.001). We also found correlation between elevated TSH and tumour size (p = 0.005). Our results suggest that in patients with nodular thyroid disease the carcinoma risk rose in parallel with serum TSH concentration, with significant increases evident in patients with serum TSH greater than 1.64 mU/L.