Endocrinology · Medical Literature
The effect of iodinated contrast media on thyroid (dys)function in children.
Abstract
Excess iodine from iodinated contrast media (ICM) can lead to thyroid dysfunction. Children, especially neonates and premature infants, may be more vulnerable due to their immature thyroid physiology. A systematic review was conducted using EMBASE, MEDLINE (PubMed), Cochrane, Web of Science, and Scopus. Inclusion criteria were studies in children ≤ 18 years receiving ICM and that reported effects on thyroid function. Exclusion criteria included topical iodine exposure, prenatal administration, and irrelevant endpoints. Case reports, reviews, and abstracts were also excluded. Most studies reported temporary thyroid function disturbances following ICM exposure in children, particularly subclinical hypothyroidism. Overt hypothyroidism was rare and occurred mainly in neonates and high-risk groups. In certain studies, up to 25% of neonates showed TSH abnormalities, with a subset requiring levothyroxine treatment. Although even more rare, some studies also reported cases of thyrotoxicosis after ICM exposure. ICM exposure can lead to thyroid dysfunction in children, especially in neonates, preterm infants, and those with risk factors. Risk-based screening and monitoring are recommended to allow timely detection and treatment.
Clinical relevance
In children aged 18 years and younger receiving iodinated contrast media (ICM), what is the incidence, spectrum, and clinical significance of thyroid dysfunction, and which subpopulations are at greatest risk? __SNAPSHOT__ {"studyDesign":"Systematic review (no meta-analysis reported)","setting":"Multi-database search: EMBASE, MEDLINE (PubMed), Cochrane, Web of Science, and Scopus; specific institutional settings of included studies not reported in abstract","sampleSize":"Not reported in abstract; number of included studies not specified","population":"Children ≤18 years of age receiving iodinated contrast media (ICM) and with reported thyroid function outcomes; special focus on neonates and premature infants","intervention":"Exposure to iodinated contrast media (ICM) via any route (route-specific breakdown not detailed in abstract)","comparator":"Not applicable for all included studies; some included studies may have had comparison groups (not specified in abstract)","primaryOutcome":"Effects on thyroid function following ICM exposure in children, including subclinical hypothyroidism, overt hypothyroidism, and thyrotoxicosis","followUp":"Not reported","fundingSource":"Not reported"}
Key findings
The systematic review found that most included studies reported temporary thyroid function disturbances following ICM exposure in children, with subclinical hypothyroidism as the predominant pattern. Overt hypothyroidism was characterized as rare and occurred mainly in neonates and high-risk groups. In certain studies, up to 25% of neonates exhibited TSH abnormalities, with a subset requiring levothyroxine treatment — though the proportion requiring treatment and specific TSH thresholds are not quantified beyond this in the abstract. Cases of thyrotoxicosis following ICM exposure were also reported, described as even rarer than overt hypothyroidism. No pooled effect sizes, odds ratios, confidence intervals, or p-values are reported in the abstract. The absolute risk of overt or persistent thyroid dysfunction across the broader pediatric population appears low based on the descriptive language used, but the 25% TSH abnormality rate in certain neonatal cohorts represents a clinically meaningful signal. No NNT or NNH can be calculated from the data provided in the abstract.
Practice implications
This systematic review consolidates evidence that ICM exposure can induce transient thyroid dysfunction in children, most commonly subclinical hypothyroidism, with the greatest risk concentrated in neonates, preterm infants, and those with underlying comorbidities (e.g., congenital cardiac disease, very low birth weight). The finding that up to 25% of neonates in certain study populations showed TSH abnormalities is consistent with prior reviews and the 2022 FDA Drug Safety Communication recommending thyroid monitoring in children up to 3 years of age after IV ICM. The physiological basis is well-established: excess iodine triggers the Wolff-Chaikoff effect, and immature thyroid glands in neonates and preterm infants may fail to escape this effect, resulting in prolonged suppression of thyroid hormone synthesis. However, several important caveats apply: (1) only the abstract was available for this summary, so details on study quality, risk of bias assessment, number and type of included studies, and heterogeneity of populations and ICM routes are unavailable; (2) the review does not appear to perform meta-analysis, limiting quantitative synthesis; (3) the boundary between statistically detected TSH abnormalities and clinically meaningful hypothyroidism requiring treatment is not uniformly defined across included studies; (4) older children and adolescents appear substantially less vulnerable, though this was not formally stratified in the abstract. Risk-based screening and monitoring are recommended by the authors, consistent with current FDA and multi-society guidance. Practice should incorporate structured post-ICM TSH surveillance in neonates and high-risk infants, but this recommendation is already embedded in existing regulatory and professional society frameworks. __LIMITATIONS__ Only the abstract was available; full methodological details — including PRISMA adherence, risk-of-bias tools, and completeness of database searches — cannot be evaluated.,No meta-analysis was performed; findings are descriptive and subject to heterogeneity across included studies in design, ICM dose/route, patient age, and thyroid function thresholds.,Case reports, reviews, and abstracts were excluded, but the remaining study base likely contains substantial observational data with varying degrees of selection bias and confounding.,Prenatal ICM administration and topical iodine exposure were excluded, which limits the generalizability of findings to intravascular and enteral ICM only.,The 25% neonatal TSH abnormality figure derives from 'certain studies,' suggesting this is not a consistent cross-study estimate but a peak from selected high-risk cohorts — the overall population-level estimate may be considerably lower.,The proportion of neonates with TSH abnormalities who actually required and received levothyroxine is not quantified, limiting NNH estimation.,Long-term neurodevelopmental outcomes of transient ICM-induced thyroid dysfunction are not addressed in the abstract.,Funding sources are not disclosed, introducing potential for undisclosed conflicts of interest.,Generalizability across different ICM agents, doses, and administration routes is unclear. __BOTTOM_LINE_CATEGORY__ confirmatory __BOTTOM_LINE__ This systematic review confirms that ICM exposure in children causes predominantly transient subclinical hypothyroidism, with neonates and preterm infants at greatest risk — including TSH abnormalities in up to 25% of neonates in higher-risk study populations. Overt hypothyroidism is rare but clinically important given the risk of neurodevelopmental harm, and risk-stratified TSH monitoring post-ICM is warranted in this population, consistent with existing FDA guidance. Confirmatory prospective controlled studies with standardized thyroid function thresholds, defined follow-up intervals, and neurodevelopmental endpoints are still needed.