Levothyroxine
A synthetic version of the thyroid hormone thyroxine (T4), levothyroxine replaces or supplements what an underactive thyroid gland fails to produce. Once absorbed, it is converted in tissues to the more active hormone and restores the signaling that regulates metabolism, energy use, growth, and the function of many organs. It is the standard treatment for hypothyroidism and is also used to suppress hormone signaling after thyroid cancer. An iodine-rich small molecule (C15H11I4NO4, molecular weight near 777) that mirrors the body's own T4, it has a long half-life of about 6 to 7 days, so blood levels change slowly and dose adjustments are assessed over weeks. That stability allows steady once-daily replacement. Levothyroxine is an approved hormone therapy and one of the most commonly dispensed medicines worldwide.
A synthetic form of the thyroid hormone T4 used to treat hypothyroidism and thyroid cancer. It replaces or supplements the body's natural thyroid hormone production, regulating metabolism, energy, and many organ functions.
Peso molecular
776,8700 g/mol
LogP
2,40
TPSA
92,80 Ų
Regla de cinco de Lipinski
Cumple
Áreas terapéuticas
Clases de fármacos
Mecanismo de acción
Synthetic thyroid hormone T4 replacement.
Pharmacokinetics (PK)
Pharmacodynamics (PD)
Synthetic thyroid hormone T4 replacement.
Estructura 2D
Cite this structure
Embed this structure
SMILES
N[C@@H](Cc1cc(I)c(Oc2cc(I)c(O)c(I)c2)c(I)c1)C(=O)O
InChI
InChI=1S/C15H11I4NO4/c16-8-4-7(5-9(17)13(8)21)24-14-10(18)1-6(2-11(14)19)3-12(20)15(22)23/h1-2,4-5,12,21H,3,20H2,(H,22,23)/t12-/m0/s1
Molecular Formula
C15H11I4NO4
HBD / HBA
3 / 5
Enlaces Rotables
5
Átomos Pesados
24
Long-term metformin use has been associated with modest reductions in TSH levels independent of levothyroxine dose, potentially complicating thyroid function monitoring in diabetic patients.
Supraphysiologic doses of corticosteroids such as prednisone can suppress TSH secretion and reduce T4-to-T3 conversion, complicating thyroid function interpretation during steroid courses.
Omeprazole raises gastric pH, which impairs the dissolution and absorption of levothyroxine, resulting in reduced thyroid hormone bioavailability and potential hypothyroid relapse.
Like all PPIs, pantoprazole reduces gastric acid and impairs levothyroxine tablet dissolution, leading to decreased T4 absorption and potentially under-treated hypothyroidism.
Sertraline can increase levothyroxine clearance, particularly in patients with pre-existing hypothyroidism, potentially necessitating levothyroxine dose increases.
Levothyroxine enhances the catabolism of vitamin K-dependent clotting factors, amplifying warfarin's anticoagulant effect and raising the risk of bleeding when thyroid replacement is initiated or doses are increased.
Ciprofloxacin can reduce levothyroxine absorption through complex formation and potential effects on gut motility and transport, risking under-replacement in hypothyroid patients on long courses.
Carbamazepine induces hepatic CYP enzymes involved in thyroid hormone metabolism, increasing levothyroxine clearance and potentially causing hypothyroid relapse in patients on replacement therapy.
No side effects recorded
Side effect data is not yet available for this drug.
Preguntas frecuentes
A synthetic form of the thyroid hormone T4 used to treat hypothyroidism and thyroid cancer. It replaces or supplements the body's natural thyroid hormone production, regulating metabolism, energy, and many organ functions.
Synthetic thyroid hormone T4 replacement.
Key pharmacokinetic parameters for Levothyroxine: Half-life: 6-7 days.
Yes, Levothyroxine is an approved drug. It has reached clinical phase 4. It is classified as a Small molecule.
Related Drugs
Same Drug Class
References & Data Sources
- ChEMBL — European Bioinformatics Institute (EBI). CHEMBL1624. Open-access bioactivity database.
- PubChem — National Center for Biotechnology Information (NCBI). CID 5819. Chemical information database.
Data aggregated from publicly available pharmacological databases. Last updated 2026-03-04.
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