Reference+

Brent, G. A. (2012). Mechanisms of thyroid hormone action. The Journal of Clinical Investigation, 122(9), 3035–3043. https://doi.org/10.1172/JCI60047


Blue: Important conclusions

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The structure of TRα and TRβ are similar in the DNA and ligand domains and differ most in the amino terminus, and it is thought that the increased potency of TRα is related to its amino terminus (34). Fundamental differences in the ligand-binding pocket have permitted the design of ligands that specifically interact with TRα or TRβ (35), and these have been important tools in the dissection of isoform-specific actions.

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Rodents derive circulating T3 primarily by the action of type 1 5′-deiodinase (D1), but humans rely primarily on D2 (1).

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Thyroid hormone is hydrophobic and was long thought to enter into the cytoplasm by passive diffusion. Thyroid hormone transporters, such as the monocarboxylate (MCT) family and organic anion transporters (OATPs), were identified based on measurable in vitro activity, but the physiologic significance of these transporters was not established early on (17). MCT8 was identified as a specific transporter of thyroid hormone and was reported to be located on the X chromosome

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a mouse model with MCT8 inactivation demonstrated that MCT8 is also important for secretion of thyroid hormone (56)

Yellow: Interesting

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Purple: To learn more

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Individuals with an MCT8 mutation have myelination delays, which are thought to be caused by impaired thyroid hormone action on oligodendrocytes (59).