TSH level as a risk factor of thyroid malignancy for nodules in euthyroid patients.

Objective: With the increased prevalence of incidental thyroid cancer, determining the predictors of thyroid malignancy has become a source of debate. This study aimed to determine the impact of thyroid stimulating hormone (TSH) levels on rates of thyroid cancer in euthyroid patients.

Methods: A retrospective study included 421 patients who underwent thyroidectomy at a tertiary hospital between 2016 and 2020. Patients' demographics, history of cancer, pre-operative workup and final histology reports were obtained. The study sample was divided into two groups based on the final histopathology (benign vs malignant). The two groups were compared using the appropriate statistical tests to determine the predictors of thyroid cancer in euthyroid patients.

Results: TSH levels were significantly higher in patients with malignant nodules compared to those with benign nodules (1.94 vs 1.62, p = 0.002). It was 1.54 times more likely for thyroid nodules to be malignant when TSH levels were higher (p = 0.038). Meanwhile, larger nodules (> 4 cm) were significantly more prevalent in benign nodules (43.1%) than in malignant nodules (21.1%). Larger nodules decreased the possibility of thyroid cancer by 24% (OR = 0.760, p-value = 0.004).

Conclusions: High TSH levels in euthyroid patients were significantly correlated with the risk of thyroid malignancy. In addition, as Bethesda category proceeded toward malignancy, TSH levels increased. High TSH levels and small nodule diameters can be used as additional parameters in predicting thyroid cancer in euthyroid patients.