Risks of Iodine Excess

Area of Science:

• Endocrinology
• Nutritional Science
• Radiology

Background:

• Iodine is essential for thyroid hormone synthesis.
• The body utilizes an iodide cycle within thyroid follicular cells for hormone production.
• Iodine sources include diet, supplements, amiodarone, and iodinated contrast media.

Purpose of the Study:

• To review the association between excessive iodine intake and thyroid dysfunction.
• To focus on iodinated contrast media as a significant source of excess iodine.
• To summarize risks in vulnerable populations and discuss potential nonthyroidal health effects.

Main Methods:

• Review of literature on iodine status assessment (urinary iodine, thyroglobulin, TSH, thyroid volume).
• Analysis of Wolff-Chaikoff and Jod-Basedow phenomena in iodine-induced thyroid dysfunction.
• Examination of guidelines for screening and monitoring contrast-induced thyroid dysfunction.

Main Results:

• Excessive iodine intake, especially from contrast media, can trigger hypothyroidism or hyperthyroidism in susceptible individuals.
• Vulnerable populations face heightened risks from iodine excess.
• Potential long-term nonthyroidal health risks associated with excess iodine warrant further investigation.

Conclusions:

• Excessive iodine exposure, particularly via iodinated contrast media, poses a risk for thyroid dysfunction.
• Current guidelines address screening and monitoring for contrast-induced thyroid dysfunction.
• More data is required to establish safe upper iodine intake limits for high-risk groups.