L-T3 and L-T4 Equivalency: Reference List

Chopra et al-1973Part 1:

Five historical voices say: “No, 25 mcg of L-T3 Liothyronine isn’t equivalent to 100 mcg L-T4

Part 2:

Contemporary thyroid science: “L-T3 pharmaceutical equivalency, Part 2: New thyroid science


Pharmaceutical monographs

Armour Thyroid web page: https://www.rxlist.com/armour-thyroid-drug.htm#description

Erfa Thyroid monograph, page 8 https://pdf.hres.ca/dpd_pm/00034857.PDF

Pfizer Cytomel monograph, page 12 https://www.pfizer.ca/sites/default/files/201710/Cytomel_PM.pdf

Mylan Synthroid monograph, page 25 https://www.mylan.ca/-/media/mylanca/documents/english/product%20pdf/1.3.1-synthroid-pm.pdf

Thyroid scientific literature

Bianco, A. C., Dumitrescu, A., Gereben, B., Ribeiro, M. O., Fonseca, T. L., Fernandes, G. W., & Bocco, B. M. L. C. (2019). Paradigms of Dynamic Control of Thyroid Hormone Signaling. Endocrine Reviews, 40(4), 1000–1047. https://doi.org/10.1210/er.2018-00275

Biondi, B., & Wartofsky, L. (2014). Treatment with thyroid hormone. Endocrine Reviews, 35(3), 433. https://doi.org/doi: 10.1210/er.2013-1083

Celi, F. S., Zemskova, M., Linderman, J. D., Babar, N. I., Skarulis, M. C., Csako, G., … Pucino, F. (2010). The pharmacodynamic equivalence of levothyroxine and liothyronine. A randomized, double blind, cross-over study in thyroidectomized patients. Clinical Endocrinology, 72(5), 709–715. https://doi.org/10.1111/j.1365-2265.2009.03700.x

Celi, F. S., Zemskova, M., Linderman, J. D., Smith, S., Drinkard, B., Sachdev, V., … Pucino, F. (2011). Metabolic effects of liothyronine therapy in hypothyroidism: A randomized, double-blind, crossover trial of liothyronine versus levothyroxine. The Journal of Clinical Endocrinology and Metabolism, 96(11), 3466–3474. https://doi.org/10.1210/jc.2011-1329

Chopra, I. J., Solomon, D. H., & Teco, G. N. C. (1973). Thyroxine: Just a Prohormone or a Hormone Too? The Journal of Clinical Endocrinology & Metabolism, 36(6), 1050–1057. https://doi.org/10.1210/jcem-36-6-1050

da Silva Teixeira, S., Filgueira, C., Sieglaff, D. H., Benod, C., Villagomez, R., Minze, L. J., … Nunes, M. T. (2017). 3,5-diiodothyronine (3,5-T2) reduces blood glucose independently of insulin sensitization in obese mice. Acta Physiologica (Oxford, England), 220(2), 238–250.

Davis, P. J., Davis, F. B., Mousa, S. A., Luidens, M. K., & Lin, H.-Y. (2011). Membrane receptor for thyroid hormone: Physiologic and pharmacologic implications. Annual Review of Pharmacology and Toxicology, 51, 99–115. https://doi.org/10.1146/annurev-pharmtox-010510-100512

Davis, P. J., Tang, H.-Y., Hercbergs, A., Lin, H.-Y., Keating, K. A., & Mousa, S. A. (2018). Bioactivity of Thyroid Hormone Analogs at Cancer Cells. Frontiers in Endocrinology, 9. https://doi.org/10.3389/fendo.2018.00739

Diana, T., Krause, J., Olivo, P. D., König, J., Kanitz, M., Decallonne, B., & Kahaly, G. J. (2017). Prevalence and clinical relevance of thyroid stimulating hormone receptor-blocking antibodies in autoimmune thyroid disease. Clinical & Experimental Immunology, 189(3), 304–309. https://doi.org/10.1111/cei.12980

Dietrich, J. W., Landgrafe, G., & Fotiadou, E. H. (2012). TSH and Thyrotropic Agonists: Key Actors in Thyroid Homeostasis. Journal of Thyroid Research, 2012. https://doi.org/10.1155/2012/351864

Dietrich, J. W., Tesche, A., Pickardt, C. R., & Mitzdorf, U. (2004). Thyrotropic Feedback Control: Evidence for an Additional Ultrashort Feedback Loop from Fractal Analysis. Cybernetics and Systems, 35(4), 315–331. https://doi.org/10.1080/01969720490443354

Escobar-Morreale, H. F., Obregón, M. J., Hernández, A., Escobar del Rey, F., & Morreale de Escobar, G. (1997). Regulation of Iodothyronine Deiodinase Activity as Studied in Thyroidectomized Rats Infused with Thyroxine or Triiodothyronine. Endocrinology, 138(6), 2559–2568. https://doi.org/10.1210/endo.138.6.5212

Feldt-Rasmussen, U., & Rasmussen, Å. K. (2007). Thyroid Hormone Transport and Actions. Diseases of the Thyroid in Childhood and Adolescence, 11, 80–103. https://doi.org/10.1159/000098021

Fröhlich, E., & Wahl, R. (2017). Thyroid Autoimmunity: Role of Anti-thyroid Antibodies in Thyroid and Extra-Thyroidal Diseases. Frontiers in Immunology, 8. https://doi.org/10.3389/fimmu.2017.00521

Fu, J., Fujisawa, H., Follman, B., Liao, X.-H., & Dumitrescu, A. M. (2017). Thyroid Hormone Metabolism Defects in a Mouse Model of SBP2 Deficiency. Endocrinology, 158(12), 4317–4330. https://doi.org/10.1210/en.2017-00618

Gereben, B., McAninch, E. A., Ribeiro, M. O., & Bianco, A. C. (2015). Scope and limitations of iodothyronine deiodinases in hypothyroidism. Nature Reviews. Endocrinology, 11(11), 642–652. https://doi.org/10.1038/nrendo.2015.155

Green, W. L. (1968). Guidelines for the Treatment of Myxedema. Medical Clinics of North America, 52(2), 431–450. https://doi.org/10.1016/S0025-7125(16)32935-2

Groeneweg, S., Peeters, R. P., Visser, T. J., & Visser, W. E. (2017). Triiodothyroacetic acid in health and disease. The Journal of Endocrinology, 234(2), R99–R121. https://doi.org/10.1530/JOE-17-0113

Groeneweg, S., Peeters, R. P., Moran, C., Stoupa, A., Auriol, F., Tonduti, D., … Visser, W. E. (2019). Effectiveness and safety of the tri-iodothyronine analogue Triac in children and adults with MCT8 deficiency: An international, single-arm, open-label, phase 2 trial. The Lancet Diabetes & Endocrinology, 7(9), 695–706. https://doi.org/10.1016/S2213-8587(19)30155-X

Inamo, Y. (2011). A 5-year-old boy with atrophic autoimmune thyroiditis caused by thyroid-stimulation blocking antibodies. Journal of Pediatric Endocrinology & Metabolism: JPEM, 24(7–8), 591–594.

Ito, M., Kawasaki, M., Danno, H., Kohsaka, K., Nakamura, T., Hisakado, M., … Miyauchi, A. (2019). Serum Thyroid Hormone Balance in Levothyroxine Monotherapy-Treated Patients with Atrophic Thyroid After Radioiodine Treatment for Graves’ Disease. Thyroid: Official Journal of the American Thyroid Association. https://doi.org/10.1089/thy.2019.0135

Ito, M., Miyauchi, A., Hisakado, M., Yoshioka, W., Ide, A., Kudo, T., … Amino, N. (2017). Biochemical Markers Reflecting Thyroid Function in Athyreotic Patients on Levothyroxine Monotherapy. Thyroid, 27(4), 484–490. https://doi.org/10.1089/thy.2016.0426

Ito, M., Miyauchi, A., Hisakado, M., Yoshioka, W., Kudo, T., Nishihara, E., … Nakamura, H. (2019). Thyroid function related symptoms during levothyroxine monotherapy in athyreotic patients. Endocrine Journal. https://doi.org/10.1507/endocrj.EJ19-0094

Ito, M., Miyauchi, A., Morita, S., Kudo, T., Nishihara, E., Kihara, M., … Amino, N. (2012). TSH-suppressive doses of levothyroxine are required to achieve preoperative native serum triiodothyronine levels in patients who have undergone total thyroidectomy. European Journal of Endocrinology, 167, 373–378. https://doi.org/DOI: 10.1530/EJE-11-1029

Jonklaas, J., & Burman, K. D. (2016). Daily Administration of Short-Acting Liothyronine Is Associated with Significant Triiodothyronine Excursions and Fails to Alter Thyroid-Responsive Parameters. Thyroid, 26(6), 770–778. https://doi.org/10.1089/thy.2015.0629

Larisch, R., Midgley, J. E. M., Dietrich, J. W., & Hoermann, R. (2018). Symptomatic Relief is Related to Serum Free Triiodothyronine Concentrations during Follow-up in Levothyroxine-Treated Patients with Differentiated Thyroid Cancer. Experimental and Clinical Endocrinology & Diabetes: Official Journal, German Society of Endocrinology [and] German Diabetes Association, 126(9), 546–552. https://doi.org/10.1055/s-0043-125064

Medina-Gomez, G., Calvo, R.-M., & Obregón, M.-J. (2004). T3 and Triac inhibit leptin secretion and expression in brown and white rat adipocytes. Biochimica Et Biophysica Acta, 1682(1–3), 38–47. https://doi.org/10.1016/j.bbalip.2004.01.007

Midgley, J. E. M., Larisch, R., Dietrich, J. W., & Hoermann, R. (2015). Variation in the biochemical response to l-thyroxine therapy and relationship with peripheral thyroid hormone conversion efficiency. Endocrine Connections, 4(4), 196–205. https://doi.org/10.1530/EC-15-0056

Refetoff, S. (1975). Thyroid Hormone Therapy. Medical Clinics of North America, 59(5), 1147–1162. https://doi.org/10.1016/S0025-7125(16)31964-2

Saberi, M., & Utiger, R. D. (1974). Serum Thyroid Hormone and Thyrotropin concentrations during thyroxine and triiodothyronine therapy. The Journal of Clinical Endocrinology & Metabolism, 39(5), 923–927. https://doi.org/10.1210/jcem-39-5-923

Selenkow, H. A., & Rose, L. I. (1976). Comparative clinical pharmacology of thyroid hormones. Pharmacology & Therapeutics. Part C: Clinical Pharmacology and Therapeutics, 1(3), 331–349. https://doi.org/10.1016/S0362-5486(76)80024-6

Snyder, P. J., & Utiger, R. D. (1972). Inhibition of thyrotropin response to thyrotropin-releasing hormone by small quantities of thyroid hormones. Journal of Clinical Investigation, 51(8), 2077–2084. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC292364/

Utiger, R. D. (1982). Differing thyrotropin responses to increased serum triiodothyronine concentrations produced by overfeeding and by triiodothyronine administration. Metabolism: Clinical and Experimental, 31(2), 180–183.

Utiger, R. D. (1988). Thyrotropin Measurements: Past, Present, and Future. Mayo Clinic Proceedings, 63(10), 1053–1056. https://doi.org/10.1016/S0025-6196(12)64925-8

Yavuz, S., Linderman, J. D., Smith, S., Zhao, X., Pucino, F., & Celi, F. S. (2013). The Dynamic Pituitary Response to Escalating-Dose TRH Stimulation Test in Hypothyroid Patients Treated With Liothyronine or Levothyroxine Replacement Therapy. The Journal of Clinical Endocrinology & Metabolism, 98(5), E862–E866. https://doi.org/10.1210/jc.2012-4196

Categories: Reference lists

2 replies


  1. No, 25 mcg of L-T3 Liothyronine isn’t equivalent to 100 mcg L-T4 – Thyroid Patients Canada
  2. L-T3 pharmaceutical equivalency, Part 2: New thyroid science – Thyroid Patients Canada

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