[Role of breast feeding in providing the newborn infant with thyroid hormones].

Radioimmunoassay was conducted to study the content of triiodothyronine and thyroxine in the human milk and in the blood serum of mature and premature newborns. It was established that with the growth of the lactation period the content of triiodothyronine and thyroxine rose; it was, respectively, 0.5 +/- 0.12 and 100.3 +/- 8.4 nmol/l in colostrum, 9.2 +/- 0.7 and 271.3 +/- 14.1 nmol/l in transient milk, 11.1 +/- 1.07 and 405.0 +/- 21.4 nmol/l in fully formed milk. Fully formed milk contains three times more triiodothyronine and thyroxine than the blood serum of newborns. The mature newborns have a sufficiently formed thyroid function. The level of thyroid hormones in the blood serum of premature newborns is decreased in proportion to the stage of their prematurity. They receive the deficient hormones through the human milk. The authors recommend that the nutrition of premature newborns receiving mixed and artificial feeding should be supplemented with thyroid hormones.