Regulatory activity has been demonstrated in two classes of iodinated organic species: thyroid hormones (T(3) and T(4)) and iodinated lipids (ILs), e.g. 6-iodo-5-hydroxy-8,11,14-eicosatrienoic acid. The formation of iodinated biomolecules requires iodide oxidation. In mammals iodide oxidation is one of several peroxidase-mediated reactions that serve to reduce hydrogen peroxide. I(2) is one of several reaction products formed by mammalian peroxidases during iodide oxidation. I(2) forms HOI in an aqueous environment which also has the capacity to iodinate organic species. This manuscript examines the potential relationship between the two classes of known mammalian iodinating species. A model describing iodination pathways for organic species in mammals is advanced. The model predicts the formation of ILs under normal dietary intake of iodine. The model was challenged by characterizing the lipids of hogs maintained on a diet containing normal levels of iodine. Iodinated lipids were found to be present in the fatty acids extracted from the thyroid of these hogs.