314 - MOTHER’S OWN MILK VS. DONOR HUMAN MILK FEEDING AND THYROID FUNCTION AT ONE MONTH OF AGE IN PREMATURE INFANTS

Publication Number: 3303.314

Mohamad Elabiad, University of Tennessee Health Science Center, Memphis, TN, United States; Heidi M. Stonecipher, University of Tennessee Health Science Center College of Medicine, Bartlett, TN, United States; Morgan Strong, University of Tennessee Health Science Center College of Medicine, Memphis, TN, United States

Background: Premature infants lose placental transfer of maternal thyroid hormones at birth and may have a transiently immature hypothalamic-pituitary-thyroid function. Thyroid hormone levels in mother's own milk (MOM) are small, but they are significantly reduced in donor human milk (DHM), likely due to pasteurization.

Objective: Hypothesis: Premature infants predominantly fed with MOM, vs. DHM, will have higher thyroid function at approximately one month of age. This study sought to determine whether predominant feeding with MOM versus DHM is associated with differences in thyroid function at approximately one month of age in premature infants.

Design/Methods: We conducted a retrospective cohort study of infants discharged from Regional One Health Hospital (Memphis, TN) between January 2021 and December 2024. Infants were included if they survived to at least one month of age and had thyroid testing around that time. Exposure groups were defined by predominant intake (≥85%) of either MOM or DHM, based on feeding records. Infants receiving mixed intake were excluded from the primary comparison. Outcomes were thyroid-stimulating hormone (TSH) and free thyroxine (free T4); Categorical variables were analyzed using chi-square tests, and continuous variables were assessed using independent t-tests or Wilcoxon-Mann-Whitney tests. Multivariate analyses adjusting for birth weight (BW) were performed to account for baseline differences.

Results: Among 262 infants evaluated, 88 met inclusion criteria (MOM: n=35; DHM: n=43). Compared to the DHM group, infants fed MOM were more mature (median GA: 29 vs. 27 weeks) and had higher birth weight (1,200 g vs. 1,030 g), with no significant differences in discharge age or weight. Thyroid testing occurred at a median of 31 days in both groups. Median TSH was modestly higher in the DHM group (2.8 vs. 2.56 mIU/L), though not statistically significant (p=0.67). Free T4 levels were significantly lower in the DHM group (1.05 vs. 1.22 ng/dL; p< 0.04), and this difference remained after adjustment for BW (Table 1).

Conclusion(s): Among premature infants, predominant MOM feeding was associated with higher free T4 and modestly lower TSH at one month compared to DHM feeding. Although TSH differences were not statistically significant, the significantly lower free T4 in the DHM group suggests a biologically meaningful effect. These findings support the prioritization of mother's own milk when available and justify prospective studies to confirm these associations and explore implications for long-term neurodevelopment.

Table 1 Results
fT4 levels were significantly higher in the breast milk group even after adjusting for birth weight.