EFFETS DE L'ABLATION DE LA THYROIDE MATERNELLE OU FOETALE SUR LE TAUX DES HORMONES CIRCULANTES CHEZ LE FOETUS DE RAT

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Abstract
The BEI [butanol extractable iodine] was determined in maternal and fetal rat plasma on day 21 of gestation by an isotope equilibrium method. The fetuses were either left intact or deprived of their thyroid gland by decapitation; the mothers were either normal or thyroidec-tomized. The thyroid gland of the fetal rat appears to be the main source of thyroid hormone present in the fetal blood: thyroidec-tomy of the mother does not alter the BEI level of normal fetuses. The ablation of the fetal thyroid gland markedly decreases the fetal BEI both in intact and thyroidectomized mothers. The BEI level in plasma of decapitated fetuses is lower in thyroidectomized mothers than in intact mothers. Hence, some maternal hormone passes through the placenta into the fetus, but this transfer is too limited to compensate for the absence of the fetal thyroid gland.