Hypothyroidism in Infants after Enteral Administration of Iodinated Contrast Media: A Rare but Serious Complication

Introduction: Excessive exposure to iodine early in life can cause primary hypothyroidism by failure to escape the Wolff-Chaikoff effect. Although reported for intravenous iodinated contrast medium (ICM) and topical iodine, prospective studies on thyroid function after enterally administered ICM are lacking. This study aimed to determine the occurrence of hypothyroidism after enteral ICM administration in young infants. Methods: Prospective cohort study was conducted between November 1st, 2022, and July 1st, 2024, in infants <6 months of age, who underwent radiological examination (mostly abdominal X-ray, AXR) with enteral ICM administration. Stasis of contrast was evaluated by AXR on day two after ICM administration. Serum thyroid-stimulating hormone (TSH) and free thyroxine (fT4) levels were measured around days 5 and 10 after ICM administration and, if abnormal, repeated on day 15. Results: Thirty-three patients were included. Seventeen patients (51.5%) were born preterm. Stasis of ICM after 2 days was present in 12 of 28 patients (42.9%). In 5 male patients (15.2%), abnormal TSH or fT4 levels were observed during follow-up. One of these 5 patients developed ICM-induced hypothyroidism requiring treatment. In 2 cases, physiological escape of the Wolff-Chaikoff effect was seen. In 2 cases, non-thyroidal illness/hypothyroxinemia of prematurity was observed. Four of the 5 patients with abnormal TSH or fT4 levels were born preterm. Conclusion: In this study, 1 patient developed primary hypothyroidism requiring levothyroxine treatment after enteral ICM administration. We recommend monitoring of thyroid function in infants younger than 6 months after enteral ICM administration, especially in preterm born infants.