Reverse triiodothyronine

Reverse triiodothyronine, also known as rT₃, is an isomer of triiodothyronine (T₃).

Reverse triiodothyronine

Names
IUPAC name O-(4-Hydroxy-3,5-diiodophenyl)-3-iodo-L-tyrosine
Systematic IUPAC name (2S)-2-Amino-3-[4-(4-hydroxy-3,5-diiodophenoxy)-3-iodophenyl]propanoic acid
Other names reverse triiodothyronine reverse T3 rT3 3,3′,5′-triiodothyronine
Identifiers
CAS Number	5817-39-0 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:11684 N
ChemSpider	559294 N
IUPHAR/BPS	2636
KEGG	C07639 N
MeSH	Reverse+triiodothyronine
PubChem CID	22069
UNII	8NZ4Y08T96 Y
CompTox Dashboard (EPA)	DTXSID50859929 DTXSID00274724, DTXSID50859929
InChI InChI=1S/C15H12I3NO4/c16-9-3-7(4-12(19)15(21)22)1-2-13(9)23-8-5-10(17)14(20)11(18)6-8/h1-3,5-6,12,20H,4,19H2,(H,21,22)/t12-/m0/s1 N Key: HZCBWYNLGPIQRK-LBPRGKRZSA-N N InChI=1/C15H12I3NO4/c16-9-3-7(4-12(19)15(21)22)1-2-13(9)23-8-5-10(17)14(20)11(18)6-8/h1-3,5-6,12,20H,4,19H2,(H,21,22)/t12-/m0/s1 Key: HZCBWYNLGPIQRK-LBPRGKRZBV
SMILES C1=CC(=C(C=C1C[C@@H](C(=O)O)N)I)OC2=CC(=C(C(=C2)I)O)I
Properties
Chemical formula	C15H12I3NO4
Molar mass	650.974
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Reverse T₃ is the third-most common iodothyronine the thyroid gland releases into the bloodstream, at 0.9%; tetraiodothyronine (levothyroxine, T₄) constitutes 90% and T₃ is 9%. However, 95% of rT₃ in human blood is made elsewhere in the body, as enzymes remove a particular iodine atom from T₄.^[1]

The production of hormone by the thyroid gland is controlled by the hypothalamus and pituitary gland. The physiological activity of thyroid hormone is regulated by a system of enzymes that activate, inactivate or simply discard the prohormone T₄ and in turn functionally modify T₃ and rT₃. These enzymes operate under complex direction of systems including neurotransmitters, hormones, markers of metabolism and immunological signals.

The levels of rT₃ increase in conditions such as euthyroid sick syndrome because its clearance decreases while its production stays the same. The decreased clearance is possibly from lower thyroxine 5-deiodinase activity in the peripheral tissue or decreased liver uptake of rT₃.^[2] In addition, increased rT₃ concentrations result from upregulated thyroxine 5-deiodinase activity in critical illness, starvation and fetal life.^[3]

Reactions

Synthesis of Reverse T₃ from T₄ via deiodination. Synthesis of T₃ and T₂ is also shown.