II. Indications

  1. Not generally recommended (no proven benefit and associated risk)
    1. Levothyroxine alone is preferred instead
    2. Levothyroxine (T4) is converted in peripheral tissues to Liothyronine (T3)
  2. May be used as an adjunct to Levothyroxine in Hypothyroidism
    1. Consider in lethargy or memory deficits despite normal TSH

III. Mechanism

IV. Medications

  1. Liothyronine (Cytomel): 5 mcg, 25 mcg and 50 mcg
  2. Levothyroxine AND Liothyronine (Liotrix) combined tabs (T4/T3): 12.5/3.1 mcg, 25/6.25 mcg, 50/12.5 mcg, 100/25 mcg, 150/37.5 mcg
    1. Rare indications, but if used typically started in adults at 12.5/3.1 or 25/6.25 and titrated every 2 weeks

V. Dosing: Adults

  1. Combined with Levothyroxine
  2. Start: 1:14 ratio of Liothyronine to Levothyroxine
    1. Example: 5 mcg Liothyronine to 75 mcg Levothyroxine
  3. Typical Dose Range: 12.5 to 25 mcg orally daily
  4. Elderly: Start at 5 mcg/day (and titrate at 5 mcg/kg increments every 1 to 2 weeks)
  5. Maximum: 100 ug orally daily

VI. Adverse Effects

  1. Risk of Cardiovascular Risks when combined with Levothyroxine
  2. See Levothyroxine

VII. Safety

  1. Pregnancy Category A
  2. Unknown safety in Lactation

VIII. Efficacy

  1. May improve neuropsychiatric symptoms
  2. Changes after replacing T3 and T4
    1. Improved mood and energy
    2. Decreased confusion, fear, and irritability
    3. No difference in TSH normalization
  3. Studies suggests no benefit
    1. Clyde (2003) JAMA 290:2952-8 [PubMed]

X. References

Images: Related links to external sites (from Bing)

Related Studies

Cost: Medications

liothyronine (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing)
LIOTHYRONINE SOD 25 MCG TAB Generic $0.37 each
LIOTHYRONINE SOD 5 MCG TAB Generic $0.29 each
LIOTHYRONINE SOD 50 MCG TAB Generic $0.53 each
cytomel (on 1/1/2023 at Medicaid.Gov Survey of pharmacy drug pricing)
CYTOMEL 5 MCG TABLET Generic $0.29 each

Ontology: Cytomel (C0010826)

Concepts Pharmacologic Substance (T121) , Amino Acid, Peptide, or Protein (T116)
MSH D014284
French Cytomel
English cytomel, Cytomel
Norwegian Cytomel

Ontology: Triiodothyronine (C0041014)

Definition (NCI) A thyroid hormone containing 3 iodine atoms generally synthesized from levothyroxine, and has greater biological activity.
Definition (NCI) A therapeutic formulation of the primary physiologically active form of endogenous thyroid hormone. In vivo, triiodothyronine enters the nucleus and binds to nuclear thyroid hormone receptors that subsequently bind to thyroid response elements (TREs) located in target genes. Receptor binding by triiodothyronine in combination with recruited coactivators results in maximal transcriptional activation after binding to TREs; in general, binding of thyroid hormone receptor alone to TREs leads to repression of gene transcription (NCI04)
Definition (NCI_NCI-GLOSS) A thyroid hormone.
Definition (MSH) A T3 thyroid hormone normally synthesized and secreted by the thyroid gland in much smaller quantities than thyroxine (T4). Most T3 is derived from peripheral monodeiodination of T4 at the 5' position of the outer ring of the iodothyronine nucleus. The hormone finally delivered and used by the tissues is mainly T3.
Definition (CSP) one of the thyroid hormones; an organic iodine containing compound secreted in small amounts by the thyroid gland; most circulating triiodothyroinine is produced by the deiodination of thyroxine in the peripheral tissues.
Definition (PDQ) A therapeutic formulation of the primary physiologically active form of endogenous thyroid hormone. In vivo, triiodothyronine enters the nucleus and binds to nuclear thyroid hormone receptors that subsequently bind to thyroid response elements (TREs) located in target genes. Receptor binding by triiodothyronine in combination with recruited coactivators results in maximal transcriptional activation after binding to TREs; in general, binding of thyroid hormone receptor alone to TREs leads to repression of gene transcription. Check for "http://www.cancer.gov/Search/ClinicalTrialsLink.aspx?id=470233&idtype=1" active clinical trials or "http://www.cancer.gov/Search/ClinicalTrialsLink.aspx?id=470233&idtype=1&closed=1" closed clinical trials using this agent. ("http://nciterms.nci.nih.gov:80/NCIBrowser/ConceptReport.jsp?dictionary=NCI_Thesaurus&code=C907" NCI Thesaurus)
Concepts Pharmacologic Substance (T121) , Hormone (T125) , Amino Acid, Peptide, or Protein (T116)
MSH D014284
SnomedCT 61275002, 350358003, 74495008, 36437009
CPT 1011720
LNC LP15922-5, MTHU003701
English Liothyronine, Triiodothyronine, triiodothyronine, L-Tyrosine, O-(4-hydroxy-3-iodophenyl)-3,5-diiodo-, 3,3',5-triiodo-L-thyronine, T3, T<sub>3</sub>, L-triiodothyronine preparation, T>3< preparation, T<sub>3</sub> preparation, T3 preparation, therapeutic triiodothyronine, L-Triiodothyronine, T AAA THYROID HORMONE 003, Triiodothyronine [Chemical/Ingredient], t3 thyroid hormone, t3, LIOTHYRONINE, T3 Thyroid Hormone, Thyroid Hormone, T3, Triiodothyronine preparation, Triiodothyronine preparation (product), Triiodothyronine T3, T-3, liothyronine, 3,5,3' Triiodothyronine, T3 - Liothyronine, Tri-iodothyronine product, T3 - Triiodothyronine, Total triiodothyronine, T>3<, Liothyronine (product), Triiodothyronine (substance), Liothyronine (substance), Triiodothyronine preparation (substance), Therapeutic T3
Swedish Trijodtyronin
Spanish liotironina, liotironina (producto), preparado con triyodotironina, tri-iodotironina, producto (producto), tri-iodotironina, producto, preparado de T3, preparado de T<sub>3</sub>, preparado con T>3<, preparado de L-triyodotironina, preparado con triyodotironina (producto), preparado con T3, preparado con T<sub>3</sub>, T3, 3, 5, 3' triyodotironina, preparado de T>3<, preparado de triyodotironina (producto), preparado de triyodotironina (sustancia), preparado de triyodotironina, tri-iodotironina, producto (sustancia), triyodotironina (sustancia), triyodotironina, Triyodotironina, Hormona Tiroidea T3, Liotironina
Czech hormon T3, trijodthyronin
Finnish Trijodotyroniini
French T3 (Hormone thyroïdienne), Tri-iodothyronine, Hormone thyroïdienne T3, Triiodothyronine, 3,5,3'-triiodothyronine, Liothyronine
Russian TRIIODTIRONIN, LIOTIRONIN, ЛИОТИРОНИН, ТРИИОДТИРОНИН
Japanese リオチロニン, フリーT3, リオサイロニン, トリヨードチロニン, トリヨードサイロニン, L-トリヨードチロニン
German T AAA SCHILDDRÜSENHORMON 003, Liothyronin, Triiodthyronin, T3-Schilddrüsenhormon
Croatian TRIJODTIRONIN
Polish Trójjodotyronina, T3, Trijodotyronina
Norwegian Liotyronine, Trijodtyronin, T3 thyreoideahormon
Portuguese Tri-Iodotironina, Hormônio T3 da Tireoide, T3, Hormônio Tireóideo T3, Liotironina
Italian Triiodotironina