What is the statistical risk of contrast-induced thyroid dysfunction, specifically the risk of contrast-induced hypothyroidism or hyperthyroidism following the administration of intravenous contrast media (IVCM)?

From the Guidelines

The risk of contrast-induced thyroid dysfunction, including both hypothyroidism and hyperthyroidism, is significantly increased following the administration of intravenous contrast media (IVCM), with odds ratios of 3.05 and 2.50, respectively, as reported in a case control study 1. The association between iodinated contrast media and thyroid dysfunction is a concern, particularly for patients undergoing contrast-enhanced CT scans.

• The odds ratio for incident overt hypothyroidism is 3.05, with a 95% confidence interval of 1.07-8.72, indicating a significant increase in risk 1.
• The odds ratio for incident overt hyperthyroidism is 2.50, with a 95% confidence interval of 1.06-5.93, also indicating a significant increase in risk 1. The median time to develop thyroid dysfunction after contrast administration is approximately 9 months, highlighting the need for prolonged monitoring of thyroid function in susceptible individuals. Key factors to consider when assessing the risk of contrast-induced thyroid dysfunction include:
• Pre-existing thyroid conditions, such as Graves' disease or multinodular goiter
• Iodine deficiency
• Autoimmune thyroid disease
• Elderly patients Judicious use of contrast media is essential, and thyroid function tests should be monitored before and after contrast administration in high-risk patients to detect any abnormalities requiring intervention 1.

From the Research

Statistical Risk of Contrast-Induced Thyroid Dysfunction

The statistical risk of contrast-induced thyroid dysfunction, specifically the risk of contrast-induced hypothyroidism or hyperthyroidism following the administration of intravenous contrast media (IVCM), is as follows:

• The occurrence of contrast-induced hyperthyroidism is very rare, with a reported incidence of less than 0.5% 2.
• Contrast medium-induced thyrotoxicosis is rare, and routine monitoring of thyroid function tests before contrast medium injection in patients with a normal thyroid is not indicated, even in areas where there is dietary iodine deficiency 3.
• The incidence of contrast-induced thyroid dysfunction has been difficult to interpret due to the observational and retrospective designs of most previous studies, but a prospective study found that the incidence of subclinical hypo- or hyperthyroidism or isolated low/high levels of free thyroxine (fT4) developed in 3.5% of the population with normal hormone levels pre-contrast-enhanced coronary CT angiography (CCTA) 4.
• Patients at risk of developing thyrotoxicosis after contrast medium injection are patients with Graves' disease and patients with multinodular goiter with thyroid autonomy, especially elderly patients and patients living in areas of iodine deficiency 3.
• Prophylactic treatment with sodium perchlorate and/or methimazole can prevent the onset of iodinated contrast media-induced hyperthyroidism (ICMIH) in high-risk populations administered IVCM, and prophylaxis with methimazole alone seems to be the most cost-effective option 5.

Risk Factors for Contrast-Induced Thyroid Dysfunction

The following are risk factors for contrast-induced thyroid dysfunction:

• Older patients (>60 years) with autonomous thyroid and concomitant cardiac diseases are at particular risk of developing hyperthyroidism 2.
• Patients with Graves' disease and patients with multinodular goiter with thyroid autonomy, especially elderly patients and patients living in areas of iodine deficiency, are at risk of developing thyrotoxicosis after contrast medium injection 3.
• Elevated thyroid peroxidase antibodies (TPOab) and being born outside Sweden were risk factors for developing subclinical hypothyroidism 4.
• Higher plasma creatinine levels at admission, higher baseline TSH levels, and lower baseline FT4 levels were associated with a higher risk of developing ICMIH 5.

Prevention and Treatment of Contrast-Induced Thyroid Dysfunction

The following are measures for the prevention and treatment of contrast-induced thyroid dysfunction:

• Identification of patients at risk of developing iodine-induced hyperthyroidism and carrying out further thyroid diagnostic procedures prior to contrast medium use 2.
• Prophylaxis with perchlorate and/or thionamides is recommended for patients at risk of developing ICMIH, or alternatively, careful monitoring of the patients after use of contrast medium 2.
• Prophylactic treatment with methimazole alone seems to be the most cost-effective option for preventing ICMIH in high-risk populations administered IVCM 5.