ESPE Abstracts

Background: Hypothyroidism is a well-known treatable cause of global developmental delay in developing children. In recent years contrast imaging studies are much more commonly employed as diagnostic means in the treatment of various pediatric conditions. In 2022, the FDA issued a warning recommending thyroid function monitoring in babies and young children who receive injections of iodine-containing contrast media(ICM) for medical imaging. They recommend the thyroid function to be checked within 3 weeks of exposure to ICM. This is based on several studies observing hypothyroidism in children after iodinated contrast use. The pathophysiology is believed to be due to a prolonged Wolff-Chaikoff effect, an autoregulatory phenomenon in which the thyroid gland inhibits thyroid hormone synthesis within the follicular cells after the body is exposed to a large amount of iodine. The immaturity of the young children’s thyroid tissue is believed to lack the ability to “escape” the Wolff-Chaikoff effect and hence the patient develops prolonged hypothyroidism.

Methods: This is a retrospective single-center study. A clinical workflow was adopted in the territory-wide pediatric hospital of Hong Kong in patients from birth – 3 years of age, where their blood thyroid function test (TSH and free T4) were checked 3 weeks after they have been administered ICM in contrast CT or contrast angiography exam in the radiology department. This includes patients from all subspecialties. The blood results are retrospectively collected and analysed to identify the prevalence of abnormal thyroid function test.

Results: A total of 117 imaging episodes were performed within a 5 month period. 49% are boys and 51% are girls. Mean age of the patient cohort is 17.7 months (SD +/- 12.5months). 81 patients were scanned. 6 (7.4%) patients with abnormal thyroid function test were identified. 1 (1.2%)of them developed persistent hypothyroidism requiring thyroxine treatment. 2(2.5%) of them had their thyroid function test repeated 2 weeks later which subsequently normalized. 3(3.7%) cases with abnormal thyroid function test were lost to follow-up.

Discussion: The results of this retrospective study shows that young children are indeed prone to develop hypothyroidism after exposure to ICM. Clinicians are recommended be wary of this risk and monitor susceptible patient groups accordingly. It is also worthwhile for clinicians and radiologists to consider this extra layer of risk against the benefit of perform contrast-enhanced imaging studies for young patients.