Hyperthyroidism was thought to lower thyroid cancer risk due to TSH suppression, potentially leading to overlooked diagnoses. This study examines clinical factors linked to thyroid cancer in hyperthyroid patients who have undergone thyroidectomy.

This study determined the clinical factors associated with malignancy among patients with hyperthyroidism who underwent thyroidectomy in a tertiary hospital.

This analytical cross-sectional study reviewed electronic biopsy results of adult patients who underwent thyroidectomy from January 2009 to December 2019 for hyperthyroidism secondary to Graves’ Disease, Solitary Toxic Adenoma or Multinodular Toxic Goiter. It considered factors linked to thyroid cancer, its prevalence, and clinical features associated with aggressive tumor behavior.

Sixty hyperthyroid patients who underwent thyroidectomy were included, 12 of whom have thyroid cancer. Each increase in the initial free thyroxine (FT4) leads to increased likelihood of thyroid cancer by 1.02 times (95% CI 1.001-1.03, p=0.044). The presence of thyroid nodule is associated with 24 times (95% CI 2.67-3275.62, p=0.002) higher risk of thyroid cancer, while every unit increase in mm for nodule diameter increases thyroid cancer odds by 1.04 times (95% CI 1.01-1.07, p=0.022). An FNAB pre-op diagnosis of malignancy is associated with having histopathologic diagnosis of thyroid cancer increased by 40 times (95% CI 2.42-6668.98, p=0.007). Although aggressive tumor behavior was noted among those with a younger age on average (36.35 vs 46.75 years), higher initial FT4 (95.97 vs 23.55 pmol/L), and those with sizeable diameter of multinodular goiter (95 mm vs 20 mm), only the high FT4 was statistically significant.

Initial FT4, thyroid nodules, nodule size, and pre-operative FNAB finding of a malignancy were the factors associated with thyroid cancer in hyperthyroid patients who underwent thyroidectomy. Furthermore, those with aggressive tumor behavior had higher initial FT4 levels.