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Plasma levels were measured of T4, free T4, T3, TSH in 64 premature neonates and in 41 those born at right time during the time-related course of the neonatal period. The results secured permit regarding the thyroid hypohormonosis syndrome in premature neonates as a consequence of the hypothalamic-hypophyseal-thyroid axis deficiency and of immaturity of the thyreostatic receptors as well. On the one hand, this promotes hypometabolism and, correspondingly, favours more economic utilization of bodily energy resources but on the other hand, such adaptation is not infrequently results in its failure and persistent thyrodeficiency, especially in very low-birth weight infants, during the whole of the neonatal period.

In order to evaluate the morphologic-and-functional state of the hypophysis-thyroid system long after the Chernobyl accident we examined 1491 children from the northern territories of the Zhitomir region. Of these, 261 had not been in utero exposed to radioiodine, 1230 pediatric subjects proved to be postconception-exposed. In utero radioiodine has not been found to affect the thyroid size in any noticeable way. The degree of structural-and-functional indices for the thyreostat system in prenatally irradiated children depends on the stage of the thyroid development just when there happened to be an exposure to radioiodine.