Reverse triiodothyronine

reverse T3triiodothyronine, reverse3,3',5'-triiodothyroninereverse T 3 rT3
Reverse triiodothyronine (3,3’,5’-triiodothyronine, reverse T 3, or rT 3 ) is an isomer of triiodothyronine (3,5,3’ triiodothyronine, T 3 ).wikipedia
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Triiodothyronine

T 3 T3triiodothyronine (T3)
Reverse triiodothyronine (3,3’,5’-triiodothyronine, reverse T 3, or rT 3 ) is an isomer of triiodothyronine (3,5,3’ triiodothyronine, T 3 ).

Euthyroid sick syndrome

non-thyroidal illness syndromeLow-T3 syndromenonthyroidal illness syndrome
The levels of rT3 increase in conditions such as euthyroid sick syndrome because its clearance decreases while its production stays the same.
The most common hormone pattern in NTIS (non-thyroidal illness syndrome) is low total and free T3, elevated rT3, and normal T4 and TSH levels, although T4 and TSH suppression may occur in more severe or chronic illness.

Thyroxine 5-deiodinase

DIO3Dlk1-Dio3 geneType III iodothyronine deiodinase
The decreased clearance is possibly from lower Thyroxine 5-deiodinase activity in the peripheral tissue or decreased liver uptake of rT3.
It catalyzes the inactivation of thyroid hormone by inner ring deiodination of the prohormone thyroxine (T 4 ) and the bioactive hormone 3,3',5-triiodothyronine (T 3 ) to inactive metabolites, 3,3',5'-triiodothyronine (RT 3 ) and 3,3'-diiodothyronine (T 2 ), respectively.

Isomer

isomersisomerismisomeric
Reverse triiodothyronine (3,3’,5’-triiodothyronine, reverse T 3, or rT 3 ) is an isomer of triiodothyronine (3,5,3’ triiodothyronine, T 3 ).

Levothyroxine

Synthroidlevothyroxine sodiumLevothroid
Reverse T 3 is the third-most common iodothyronine the thyroid gland releases into the bloodstream, of which 0.9% is rT 3 ; tetraiodothyronine (levothyroxine, T 4 ) constitutes 90% and T 3 is 9%.

Enzyme

enzymologyenzymesenzymatic
However, 95% of rT 3 in human blood is made elsewhere in the body, as enzymes remove a particular iodine atom from T 4.

Iodine

II 2 iodinated
However, 95% of rT 3 in human blood is made elsewhere in the body, as enzymes remove a particular iodine atom from T 4.

Hypothalamus

hypothalamicanterior hypothalamushypothalamic hormones
The production of hormone by the thyroid gland is controlled by the hypothalamus and pituitary gland.

Pituitary gland

pituitaryhypophysishypophysis cerebri
The production of hormone by the thyroid gland is controlled by the hypothalamus and pituitary gland.

Sum activity of peripheral deiodinases

SPINA-GDcalculated sum activity of peripheral deiodinases (SPINA-GD)deiodinase activity
Additionally, it is not possible to differentiate step-up reactions resulting in T3 production from the step-down reaction catalyzed by type 3 deiodination, which mediates production of reverse T3.

Iodine in biology

iodineProtective effects of iodine on breast cancertrace iodines
These enzymes also convert T4 to reverse T3 (rT3) by removing an inner ring iodine atom, and also convert T3 to 3,3'-Diiodothyronine (T2) by removing an inner ring atom.

Thyroid

thyroid glandthyroid folliclethyroid function
The iodinated tyrosines are cleaved, forming the thyroid hormones T 4, T 3, DIT, MIT, and traces of reverse triiodothyronine.

Deiodinase

Deiodinase enzymesdeiodinasestetraiodothyronine 5' deiodinase
Three related isoforms, deiodinase type I, II, and III, contribute to activation and inactivation of the initially released hormone precursor T 4 (thyroxine) into T 3 (triiodothyronine) or rT 3 (reverse triiodothyronine) in target cells.