3-Iodotyrosine

3-Iodotyrosine is an intermediate in the synthesis of thyroid hormones which is derived from iodination of tyrosine at the meta-position of the benzene ring. One unit can combine with diiodotyrosine to form triiodothyronine, as occurs in the colloid of the thyroid follicle. Two units can combine to form 3,3'-diiodothyronine.
3-Iodotyrosine is a reversible inhibitor of the enzyme tyrosine hydroxylase. 
Relevance in dopamine studies.
3-Iodotyrosine, a pathway inhibitor in the synthesis of the neurotransmitter dopamine, was used to determine the effects of decreased dopamine levels in social spacing of "Drosophila melanogaster". 3-4 day old flies that were fed 3-iodotyrosine for 24 hours were shown to have altered dopamine levels.