Chemical Component Summary

Identifiers(2S)-2-amino-3-[4-(4-hydroxy-3,5-diiodo-phenoxy)-3,5-diiodo-phenyl]propanoic acid
FormulaC15 H11 I4 N O4
Molecular Weight776.87
Isomeric SMILESc1c(cc(c(c1I)Oc2cc(c(c(c2)I)O)I)I)C[C@@H](C(=O)O)N

Chemical Details

Formal Charge0
Atom Count35
Chiral Atom Count1
Bond Count36
Aromatic Bond Count12

Drug Info: DrugBank

DrugBank IDDB00451 
Groups approved
DescriptionLevothyroxine is a synthetically produced form of thyroxine, a major endogenous hormone secreted by the thyroid gland.[F4633] Also known as L-thyroxine or the brand name product Synthroid, levothyroxine is used primarily to treat hypothyroidism, a condition where the thyroid gland is no longer able to produce sufficient quantities of the thyroid hormones T<sub>4</sub> (tetraiodothyronine or thyroxine) and T<sub>3</sub> (triiodothyronine or [DB00279]), resulting in diminished down-stream effects of these hormones. Without sufficient quantities of circulating thyroid hormones, symptoms of hypothyroidism begin to develop such as fatigue, increased heart rate, depression[A179620], dry skin and hair, muscle cramps, constipation, weight gain, memory impairment, and poor tolerance to cold temperatures.[F4636,A35722] In response to Thyroid Stimulating Hormone (TSH) release by the pituitary gland, a normally functioning thyroid gland will produce and secrete T<sub>4</sub>, which is then converted through deiodination (by type I or type II 5′-deiodinases)[A179941] into its active metabolite T<sub>3</sub>. While T<sub>4</sub> is the major product secreted by the thyroid gland, T<sub>3</sub> exerts the majority of the physiological effects of the thyroid hormones; T<sub>4</sub> and T<sub>3</sub> have a relative potency of ~1:4 (T4:T3).[F4633] T<sub>4</sub> and T<sub>3</sub> act on nearly every cell of the body, but have a particularly strong effect on the cardiac system.[A179935] As a result, many cardiac functions including heart rate, cardiac output, and systemic vascular resistance are closely linked to thyroid status.[A179938] Prior to the development of levothyroxine, [DB09100] or desiccated thyroid, used to be the mainstay of treatment for hypothyroidism. However, this is no longer recommended for the majority of patients due to several clinical concerns including limited controlled trials supporting its use. Desiccated thyroid products contain a ratio of T4 to T3 of 4.2:1, which is significantly lower than the 14:1 ratio of secretion by the human thyroid gland. This higher proportion of T3 in desiccated thyroid products can lead to supraphysiologic levels of T3 which may put patients at risk of thyrotoxicosis if thyroid extract therapy is not adjusted according to the serum TSH.[A35722, F4636]
  • 3,5,3',5'-Tetraiodo-L-thyronine
  • Levothyroxine
  • L-Thyroxine
  • Levothyroxine sodium
  • T4
Brand Names
  • Synthroid Tab 88mcg USP
  • Apo-levothyroxine
  • Levotec 125mcg Tablets USP
  • Eltroxin Tab 50mcg
  • Levotec 112mcg Tablets USP
IndicationLevothyroxine is indicated as replacement therapy in primary (thyroidal), secondary (pituitary) and tertiary (hypothalamic) congenital or acquired hypothyroidism. It is also indicated as an adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer.
  • Agents used to treat hypothyroidism
  • Amino Acids
  • Amino Acids, Aromatic
  • Amino Acids, Cyclic
  • Amino Acids, Peptides, and Proteins
  • H03AA01
  • H03AA51
CAS number51-48-9

Drug Targets

NameTarget SequencePharmacological ActionActions
View More
Drug Info/Drug Targets: DrugBank 3.0: a comprehensive resource for 'omics' research on drugs. Knox C, Law V, Jewison T, Liu P, Ly S, Frolkis A, Pon A, Banco K, Mak C, Neveu V, Djoumbou Y, Eisner R, Guo AC, Wishart DS. Nucleic Acids Res. 2011 Jan; 39 (Database issue):D1035-41. | PMID:21059682

Related Resource References

Resource NameReference
Pharos CHEMBL1624
PubChem 25201348, 5819
ChEBI CHEBI:18332, CHEBI:58448