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Abstract
The deiodinases activate or inactivate thyroid hormone, and their importance in thyroid hormone homeostasis has become increasingly clear with the availability of deiodinase-deficient animals. At the same time, heightened interest in the field has been generated following the discovery that the type 2 deiodinase can be an important component in both the Hedgehog signaling pathway and the G protein–coupled bile acid receptor 1–mediated (GPBAR1-mediated) signaling cascade. The discovery of these new roles for the deiodinases indicates that tissue-specific deiodination plays a much broader role than once thought, extending into the realms of developmental biology and metabolism.
Authors
Antonio C. Bianco, Brian W. Kim
Figure 1
Basic deiodinase reactions.
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The reactions catalyzed by the deiodinases remove iodine moieties (blue spheres) from the phenolic (outer rings) or tyrosil (inner rings) rings of the iodothyronines. These pathways can activate T4 by transforming it into T3 (via D1 or D2) or prevent it from being activated by converting it to the metabolically inactive form, reverse T3 (via D1 or D3). T2 is an inactive product common to both pathways that is rapidly metabolized by further deiodination.
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ISSN: 0021-9738 (print), 1558-8238 (online)