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Thyroid Hormone Gene: Seek personalized thyroid care

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Illustration highlighting the thyroid gland.

Studying the gene identified as DIO2 (IDII) has shown that treating all cases of hypothyroidism with the same conventional methodology might not be the most effective treatment — these are two populations that react very differently to levothyroxine sodium monotherapy: while one group achieves the desired T3 levels, the other does not. For these individuals, levothyroxine sodium (T4) alone is incapable of fully remedying the symptoms of hypothyroidism: these people cannot convert their new stores of T4 into T3 (and having too much T4 without enough IDII can even make the problem worse—T4 that that doesn’t become T3 is more likely to become reverse T3 which decreases thyroid function. Adding T3, in theory, and practice, essential for these individuals. (Gavin L, Castle J, McMahon F, Martin P, Hammond M, Cavalieri R. “Extrathyroidal Conversion of Thyroxine to 3, 3’, 5’-Triiodothyronine (Reverse-T3) and to 3, 5, 3’-Triiodothyronine. Journal of clinical endocrinology and Metabolism. 1977;44(4):733-42.)

DIO2 Gene: “The protein encoded by this gene belongs to the iodothyronine deiodinase family. It catalyzes the conversion of prohormone thyroxine (3,5,3′,5′-tetraiodothyronine, T4) to the bioactive thyroid hormone (3,5,3′-triiodothyronine, T3) by outer ring 5′-deiodination. This gene is widely expressed, including in thyroid, placenta, pituitary, and brain. It is thought to be responsible for the ‘local’ production of T3, and thus important in influencing thyroid hormone action in these tissues. It has also been reported to be highly expressed in thyroids of patients with Graves disease, and follicular adenomas. The intrathyroidal T4 to T3 conversion by this enzyme may contribute significantly to the relative increase in thyroidal T3 production in these patients.” (DIO2 iodothyronine deiodinase 2 [ Homo sapiens (human) ]
Gene ID: 1734, updated on 5-Nov-2017)

Resource: Metabolism of Thyroid Hormone. Robin P. Peeters, M.D. Ph.D.
Dept. of Endocrinology, Room D-442, Erasmus University Medical Center, Wytemaweg, 3015 CE, Rotterdam The Netherlands