In a prospective study, thyroid metabolism in 102 patients undergoing diagnostic coronary angiography was investigated, stratified for thyroid morphology. The thyroid function serum parameters "TT3, rT3, TT4, fT4 and TSH" and the urinary iodine excretion were measured before and three weeks after diagnostic intraarterial administration of the iodine-containing contrast agent. Only patients with euthyroid function were included in order to answer the questions whether or not the administration of non-ionic iodine containing contrast medium leads to significant thyroid function changes in euthyroid patients and whether thyroid morphology is a prognostic factor for the risk of developing hyperthroidism. Serum concentrations of thyroid autoantibodies (TPO-Ab, Tg-Ab, TSH-receptor-Ab) were measured and thyroid ultrasound was performed. According to the ultrasound findings, 4 morphologic groups were formed: normal thyroid glands (n = 37), normal sized but nodular glands (n = 16), diffuse goiter (n = 15) and nodular goiter (n = 34). Twenty-five patients were positive for Tg-Ab; TPO-Ab were found in 13 patients. TSH-receptor-Abs were not detected in all patients. TT3 levels did not significantly change after iodine application (p = 0.30). TT4 and fT4 levels showed significantly different alterations in the 4 groups (fT4 p < 0.001). The amount of iodine given did not influence alteration of serum concentrations of TSH (p = 0.67), TT3 (p = 0.68), TT4 (p = 0.37), fT4 (p = 0.92) and rT3 (p = 0.81). Elevated levels of urinary iodine excretion correlated with the amount of contrast medium given (p = 0.087). Albeit there was a high number of nodular transformed glands and goitrous patients included, and our cohort was recruited in an iodine deficient area, we did not observe hyperthyroidism in any patient. However, thyroid function parameters are significantly altered after coronary angiography independent of antibody status and the amount of contrast agent given, but dependent on thyroid morphology.