Small molecule
PubChem CID 5819
Levothyroxine
Synthroid
- Mechanism of action
- Thyroid hormone receptor agonist
- In plain language
- Supplies the body with a lab-made copy of its own thyroid hormone, restoring the chemical signal that keeps metabolism running at a normal pace.
- How it works
- Levothyroxine sodium is synthetic L-thyroxine (T4), structurally and functionally identical to endogenous T4. Approximately 80% of circulating T4 is converted in peripheral tissues by deiodinases to triiodothyronine (T3), the more biologically active hormone. T3 diffuses into the cell nucleus and binds thyroid hormone receptor proteins complexed with DNA, activating gene transcription and downstream protein synthesis that governs metabolic rate, thermogenesis, and growth/CNS maturation. At doses above physiologic replacement, this same pathway suppresses pituitary TSH secretion, exploited therapeutically in the management of thyrotropin-dependent thyroid cancer.
- Therapeutic applications
- Replacement therapy for hypothyroidism, whether primary, secondary, or tertiary, congenital or acquired, in adult and pediatric patients including neonates. Also indicated as an adjunct to surgery and radioiodine therapy for suppression of pituitary TSH secretion in the management of thyrotropin-dependent, well-differentiated thyroid cancer. Not indicated for suppression of benign thyroid nodules or nontoxic diffuse goiter in iodine-sufficient patients.
- Class
- Small molecule
- Therapeutic area
- Endocrine
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