Iodinated contrast-induced thyrotoxicosis
Iodinated contrast-induced thyrotoxicosis is rare and may occur in patients with pre-existing thyroid disease and through complications of thyrotoxicosis (e.g. cardiac arrhythmia) may be fatal. Patients with a normal thyroid gland are unaffected.
Patients with existing thyrotoxicosis should not receive iodinated contrast 3 and high-risk patients (see below) should avoid iodinated contrast unless there is a strong indication 4.
A recent study has established a strong association between iodine contrast administration and subsequent new hyperthyroidism 1,2. Prevalence in iodine-deficient countries is estimated at 0.25-0.5% and in non-iodine deficient countries is 0.025%, although exact prevalence has yet to be determined.
Administration of iodinated contrast results in a large iodine load to the thyroid (at least 90 times the daily recommended intake), which may lead to increased secretion of thyroid hormones (see: Jod-Basedow phenomenon).
Hyperthyroidism develops over 2-12 weeks 1 and is more commonly latent (i.e. clinically silent) than overt (i.e. thyrotoxicosis) 4.
- elderly (due to the increased prevalence of nodular thyroid disease)
- people living in areas of endemic iodine deficiency
Treatment and prognosis
Various treatment schedules have been proposed for prophylaxis 4, however, it is not unanimously recommended 1. Patients at high risk, especially those with an underlying unstable cardiovascular disease, should have thyroid function tests carefully monitored after administration 1,4.
- 1. Dunne P, Kaimal N, MacDonald J et-al. Iodinated contrast-induced thyrotoxicosis. CMAJ. 2013;185 (2): 144-7. doi:10.1503/cmaj.120734 - Free text at pubmed - Pubmed citation
- 2. Andreucci M, Solomon R, Tasanarong A. Side effects of radiographic contrast media: pathogenesis, risk factors, and prevention. Biomed Res Int. 2014;2014: 741018. doi:10.1155/2014/741018 - Free text at pubmed - Pubmed citation
- 3. Thomson, Kenneth R., and D. Varma. "Safe use of radiographic contrast media." Australian Prescriber 33.1 (2010): 19-22.
- 4. van der Molen AJ, Thomsen HS, Morcos SK et-al. Effect of iodinated contrast media on thyroid function in adults. Eur Radiol. 2004;14 (5): 902-7. doi:10.1007/s00330-004-2238-z - Pubmed citation
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