Thyroxine embryonic

The thyroid hormone thyroxine (tetraiodo-thyronine, T4) and its active form triiodothyronine (T3) are derived from the amino acid tyrosine. The iodine atoms at positions 3 and 5 of the two phenol rings are characteristic of them. Post-translational synthesis of thyroxine takes place in the thyroid gland from tyrosine residues of the protein thyro-globulin, from which it is proteolytically cleaved before being released, iodothyronines are the only organic molecules in the animal organism that contain iodine. They increase the basal metabolic rate, partly by regulating mitochondrial ATP synthesis, in addition, they promote embryonic development. 

Jones, R.W., W.C. Gibson and C.J. Nickolls. Factors influencing mitotic activity and morphogenesis in embryonic development. I. The effects of thyroxine and thiouracil on the development of Brachydanio rerio (zebra fish). Anat. Rec. Ill 93, 1951. 

Escobar del Rey F, Pastor R, Mallol J, Morreale de Escobar G, Effects of maternal iodine deficiency on the L-Thyroxine and 3,5,3 -Triiodo-L-Thyronine contents of rat embryonic tissues before and after onset of fetal thyroid function. Endocrinology 118 1259 (1986)... 

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