Thyroidal Iodine and Enzymatic Defects in Cattle with Congenital Goiter

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Abstract
A herd of cattle with congenital goiter was bred selectively in a nongoitrous area. The animals were clinically euthyroid. Their thyroidal iodine concentration was only a fraction of that of normal cattle, whereas their serum protein-bound iodine was greatly elevated. The serum organic iodine behaved electrophoretically like an iodoalbumin and was partially extractable with acid butanol. The acid butanol extract of serum protein precipitates of goitrous cattle contained iodotyrosines as well as thyroxine. Iodotyrosines also appeared in urine of goitrous cattle. Homogenates prepared from goitrous thyroids showed excessive deiodinating activity per unit thyroid weight when incubated with mono- and diiodotyrosine, but had no deiodinating effect on thyroxine. Thyroidal protease activity per g of goitrous thyroid tissue was also greater than that of normal ox thyroid. (Endocrinology76: 353, 1965)

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