Effects of iodine contrast media on thyroid function - a prospective study

Area of Science:

• Radiology
• Endocrinology
• Cardiology

Background:

• Iodine contrast medium (ICM) can potentially induce thyroid dysfunction due to excess iodide.
• Previous studies on contrast-induced thyroid dysfunction (CITD) are limited by observational and retrospective designs.
• The Swedish CArdioPulmonary bioImage Study (SCAPIS) offers a prospective cohort for evaluating CITD.

Purpose of the Study:

• To prospectively assess the incidence, magnitude, and clinical impact of contrast-induced thyroid dysfunction.
• To evaluate thyroid hormone levels and thyroid-related symptoms after contrast-enhanced coronary CT angiography (CCTA).
• To identify risk factors associated with ICM-induced thyroid dysfunction.

Main Methods:

• Analysis of thyroid hormone levels before and after CCTA in 422 individuals.
• Administration of thyroid-related patient-reported outcome questionnaires (ThyPRO) to 368 participants.
• Measurement of thyroid peroxidase antibodies (TPOab) and thyroid ultrasound to detect nodules.

Main Results:

• A small, statistically significant effect on thyroid hormone levels was observed, with no overt hypo- or hyperthyroidism.
• Subclinical thyroid dysfunction or isolated free thyroxine (fT4) level changes occurred in 3.5% of individuals without increased symptoms.
• Elevated TPOab and being foreign-born were risk factors for subclinical hypothyroidism; thyroid nodules were not associated with ICM-induced dysfunction.

Conclusions:

• Contrast-induced thyroid dysfunction is rare, typically mild, self-limiting, and often asymptomatic in iodine-sufficient populations aged 50-65.
• Prospective assessment using the SCAPIS cohort provides reliable data on ICM's impact on thyroid function.
• The findings support that ICM use is generally safe concerning thyroid function in this demographic.