Background <p>This study aims to investigate the effects of iodinated contrast media (ICM) exposure on thyroid function in patients with subclinical hyperthyroidism.</p> Methods <p>The study included 46 patients with subclinical hyperthyroidism who presented to the cardiology outpatient clinic and underwent angiographic imaging procedures. Thyroid function tests (TSH, fT3, fT4) of the patients before and after the procedure were analyzed retrospectively. Patients were divided into two groups as low volume (&lt; 200&#xa0;ml) and high volume (≥ 200&#xa0;ml) according to the volume of contrast medium received. Pre- and post-procedure comparisons as well as analyses according to low and high-volume exposure were performed.</p> Results <p>After the procedure, 50% of the patients became euthyroid and 41.3% remained in the same group (subclinical hyperthyroidism). 2 patients (4.3%) developed clinical hyperthyroidism, and another 2 patients (4.3%) developed clinical hypothyroidism. TSH values increased significantly after the procedure (<i>p</i> &lt; 0.01), but no significant change was observed in fT3 and fT4 values.</p> Conclusions <p>In patients with subclinical hyperthyroidism, thyroid function mostly remained stable or became euthyroid after ICM exposure. However, a group of patients developed clinical hypothyroidism or hyperthyroidism. These results suggest that patients with subclinical hyperthyroidism should be closely monitored when using ICM. Long-term follow-up will contribute to a better understanding of the possible risks in this patient group.</p>