THE PRODUCTION OF THYROID HORMONE IN THE DAY-OLD CHICK, WITH NOTES ON THE EFFECT OF THYROTROPHIN ON THE CHICK THYROID

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Abstract
Day-old chicks are able to synthesize thyroxine, monoiodotyrosine and diiodotyrosine. These 3 amino acids appear to occur chiefly in the bound form since they could not be detected in the free state when nonhydrolyzed samples of thyroid extract were examined by paper chromatography. Small amounts of inorganic iodide were found both in unhydrolyzed thyroid and in trypsin hydrolysates. Fractionationof the thyroid hydrolysates by both column and paper chromatography showed most of the organic 1131 to be present as diiodotyrosine with decreasing amounts as monoiodotyrosine and thyroxine, and a very small percentage of triiodothyronine. After stimulation of the thyroid gland by a large dose of thyrotropin, the gland''s thyroxine content was significantly decreased.