{"entity":{"id":"levothyroxine","kind":"drug","name":"Levothyroxine","aka":["L-thyroxine","T4","thyroxine"],"tldr":"Levothyroxine replaces thyroid hormone. After surgery and radioactive iodine for thyroid cancer it is given at a dose that also keeps TSH down, and it treats the underactive thyroid that immunotherapy can cause.","summary":"The US label covers replacement in primary, secondary and tertiary hypothyroidism and pituitary TSH suppression \"as an adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer\"; it is not indicated for suppressing benign nodules. SITC 2021 states that \"The standard of care for the treatment of hypothyroidism is levothyroxine\", and that most people who develop thyrotoxicosis from checkpoint inhibitors go on to need long-term replacement. The Synthroid NDA in Drugs@FDA was approved on 24 July 2002.","status":"approved","asOf":"2026-11-11","wikipedia":"https://en.wikipedia.org/wiki/Levothyroxine","links":[{"label":"US label (DailyMed): levothyroxine sodium tablets","url":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=008de8fd-150f-4022-8ccb-c8bfa94875c7"},{"label":"Brahmer et al., SITC clinical practice guideline on immune checkpoint inhibitor-related adverse events (J Immunother Cancer 2021)","url":"https://doi.org/10.1136/jitc-2021-002435"}],"tags":["supportive","generic","supportive-care-gaps-2026-11"],"related":[],"cancers":["thyroid"],"sections":[],"technologies":[],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":["tsh-suppression","immune-endocrinopathy"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"provenance":{"editedBy":"OnCo supportive care gap fill (DailyMed, openFDA, Drugs@FDA, emc SmPCs, NICE, ESMO, ASCO, MASCC, SITC, ASTCT, ITAC, Europe PMC)","editedOn":"2026-11-11"},"brand":"Synthroid / Eltroxin","modality":"Thyroid hormone replacement (oral)","supportive":true,"mechanism":"Synthetic thyroxine (T4), converted in the body to the active hormone T3.","approvals":[{"region":"US","year":2002,"indication":"Hypothyroidism; TSH suppression with surgery and radioiodine in well-differentiated thyroid cancer","note":"Year is the Synthroid NDA 021402 approval (Drugs@FDA)"}],"mechanismSteps":[],"toxicity":[],"access":[],"regulatoryEvents":[]},"route":"/drugs/levothyroxine/","neighbours":{"cancer":[{"id":"thyroid","kind":"cancer","name":"Thyroid cancer","route":"/cancers/thyroid/"}],"term":[{"id":"immune-endocrinopathy","kind":"term","name":"Immune-related endocrinopathies (thyroiditis, hypophysitis)","route":"/terms/immune-endocrinopathy/"},{"id":"tsh-suppression","kind":"term","name":"TSH suppression","route":"/terms/tsh-suppression/"}]}}