619 - Evaluation of the Relationship Between Breast Milk Iodine Levels and Neonatal Iodine, Nitrite-Nitrate Levels and Thyroid Function Tests

Publication Number: 2604.619

Sinem Nisa Karadeli, kayseri şehir hastanesi, kayseri, Kayseri, Turkey; AHMET ÖZDEMİR, Health Sciences University Kayseri City Hospital, Kayseri, Kayseri, Turkey

Background: Maternal iodine deficiency and the development of hypothyroidism are important as they can be a cause of congenital hypothyroidism. Therefore, screening for iodine deficiency is recommended for all pregnant women. In cases of iodine deficiency, it is important to evaluate the condition with urine iodine measurement and TSH measurement.

Objective: The aim of this study was to evaluate the relationship between urinary nitrate-nitrite levels, urinary iodine levels, and breast milk iodine levels in mothers and newborns; to compare these parameters with thyroid function tests and to reveal differences by gestational age (late preterm < 38 weeks, term≥38 weeks). Furthermore, the potential effects of environmental nitrate exposure were investigated based on the region where the patients lived.

Design/Methods: This descriptive cross-sectional study was conducted on a total of 109 mother-infant pairs. Breast-milk and urine samples were collected from all participants in the postpartum period, and neonatal thyroid function tests were also recorded. Measurements included urine iodine, breast milk iodine, urine nitrate-nitrite and nitrite, and thyroid function tests. Participants were divided into two groups based on gestational age: late preterm (36-37 weeks) and term (38-41 weeks).

Results: In our study, breast milk iodine levels were found to be insufficient. Both breast milk and urine iodine levels were observed to be higher in term infants than in late preterm infants. While TSH levels tended to increase in the term group, T4 levels were relatively higher in the preterm group. Nitrate and nitrite levels were similar in both groups.
Table 1 shows the descriptive characteristics of the study group. When grouped as late preterm and term according to their gestational weeks, iodine levels, nitrite-nitrate and thyroid function tests were compared (Table 2). Mean urinary iodine levels in term newborns (27.29 ± 31.15 µg/L) were significantly higher than in late preterms (12.18 ± 7.81 µg/L) (p=0.001) (Table 2). Among thyroid function tests, Free T4 levels were statistically significantly higher in late preterm infants than in term infants (p=0.006) (Table 2).

Conclusion(s): This study demonstrates that urinary and breast milk iodine levels may be associated with thyroid function tests in mother-infant pairs. Low iodine levels in late preterm infants suggest that maternal iodine deficiency or environmental nitrate exposure may affect thyroid hormone synthesis. It is concluded that regional environmental factors, particularly soil nitrate content, may have indirect effects on neonatal thyroid function.

TABLE 3 AND 4
WhatsApp Image 2025-11-02 at 20.54.33 (1).jpegTable 3. Comparison according to mode of delivery
Table 4. Paired samples test between breast milk iodine and urine iodine

TABLE 5 AND 6
WhatsApp Image 2025-11-02 at 20.54.33.jpegTable 5. Summary of effect sizes (Cohen’s d and Hedges’ correction)
Table 6. Distribution of participants by region