Thyroid Research Thyroid Research Archive Congenital

Breast milk contains too little thyroid hormone to raise plasma thyroid hormone concentrations in preterm infants

(July 2002)

The background of the study. Breast milk may contain small amounts of thyroxine (T4) and triiodothyronine (T3). In this study plasma T4 and T3 concentrations were measured at multiple times in breast-milk-fed and formula-fed preterm infants.

How the study was done. The study subjects were preterm infants who were part of the control group of a study of the effect of T4 therapy on postnatal development. The infants were given decreasing amounts of intravenous feedings and increasing amounts of oral feedings starting at birth; by two weeks most infants received only oral feedings of expressed breast milk or formula. The infants were divided into breast-milk- and formula-fed groups on the basis of the daily intake of breast milk in relation to total intake. The breast milk group received >50 percent of their caloric intake as breast milk; the formula group received <25 percent of their caloric intake as breast milk.

Plasma T4, T3, and thyrotropin (TSH) were measured on days 7, 14, 21, 28, 35, and 42 after birth in all infants. In addition, T4 and T3 were measured in samples of milk collected from 32 mothers of preterm infants and 10 mothers of term infants, and in the formula used.

The results of the study. There were 32 infants in the breast milk group and 25 infants in the formula group. The mean plasma T4, T3, and TSH concentrations were almost identical at all six times in both groups of infants.

The concentrations of T4 in the milk of the mothers of preterm infants were very low, as was the concentration in the formula, and the concentrations were five times higher in the samples from the mothers of term infants.

The conclusions of the study. Plasma T4 and T3 concentrations are similar in preterm infants fed breast milk and formula during the first weeks of life.

The original article. Van Wassenaer AG, Stulp MR, Valianpour F, Tamminga P, Ris Stalpers C, de Randamie JS, van Beusekom C, de Vijlder JJ. The quantity of thyroid hormone in human milk is too low to influence plasma thyroid hormone levels in the very preterm infant. Clin Endocrinol 2002;56:621-7.

Thyroid Research Archive
Congenital Hypothyroidism

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