Separation and Radioimmunoassay of T3 and T4 in Human Breast Milk

Publisher Website
Google Scholar
Abstract
There is little agreement among published reports of the radioimmunoassayable thyroid hormone content of breast milk, likely due to wide variations in methodology applied. In order to achieve a higher degree of specificity in the determination of T3 [triiodothyronine] and T4 [thyroxine] concentrations in breast milk, samples were ethanol-extracted and then chromatographed on an LH-20 column. Using this method, all T3 and T4 RIA [radioimmunoassay] activity eluted with the void volume. Following pancreatin digestion and subsequent extraction of whole milk samples, void volume T3 RIA activity decreased, and T3 co-eluted primarily with a standard preparation of T3 or 125I-T3, at a concentration of 275 .+-. 132 ng/dl (mean .+-. SD) (n = 9). In contrast, the elution volume of T4 RIA activity appeared unaffected by pancreatin. Immunoreactive T3 and T4 are differentially bound to a thyroid hormone binding substance present in breast milk. They further support the hypothesis that thyroid hormone sufficient to supplement the thyroid economy of the thyroid-deficient suckling infant is present in human breast milk.