Iodine status and thyroid function in children with multiple food allergy: a prospective cross-sectional study

OBJECTIVES: Children with multiple food allergies (MFA) often follow elimination diets that restrict major dietary sources of iodine, thereby increasing the risk of iodine deficiency. This study aimed to evaluate urinary iodine concentration (UIC) and thyroid function parameters in children with MFA and to compare these findings with those of age- and sex-matched healthy controls. METHODS: In this prospective cross-sectional study, 47 children aged 0-13 years with IgE-mediated MFA on elimination diets were compared with 52 age- and sex-matched healthy controls between October 2022 and March 2024. Serum thyroid-stimulating hormone (TSH), free triiodothyronine (fT3), and free thyroxine (fT4) were measured using electrochemiluminescence immunoassay, and UIC was determined by inductively coupled plasma mass spectrometry (ICP-MS). Anthropometric parameters were also assessed. RESULTS: Serum TSH, fT3, and fT4 levels did not differ significantly between the MFA and control groups (p>0.05). However, median UIC was significantly lower in the MFA group [86 μg/L (IQR: 50-115)] compared with controls [126 μg/L (IQR: 105-134)] (p=0.001), indicating mild iodine deficiency in the MFA group. No cases of overt hypothyroidism were detected. CONCLUSIONS: Children with multiple food allergies receiving elimination diets are at increased risk of mild iodine deficiency, even in iodine-sufficient regions, although overt thyroid dysfunction may not yet be evident. These findings highlight the importance of routine monitoring of iodine status and early nutritional interventions in this vulnerable population.