Abstract
Levothyroxine (L-T4) is arguably the most prescribed medication in the United States, with its primary therapeutic indication for hypothyroidism from chronic thyroiditis or Hashimoto’s disease. Such patients are candidates for so-called replacement dosage, with the administered dosage of L-T4 titrated to a target thyrotropin (TSH) level within the normal range of 0.4–2.0 mU/L. Patients with thyroid cancer who have had near-total to total thyroidectomy are usually candidates for suppressive levothyroxine dosage, which is “so-called” because the aim of therapy is to give a slightly supraphysiologic dosage of thyroxine to suppress TSH. The rationale for suppressive therapy is based on studies indicating that TSH stimulation enhances tumor growth, TSH serving as a growth factor or mitogen for thyroid malignancies with observations of more rapid tumor growth seen clinically after thyroxine withdrawal. The growth-promoting property of TSH is presumed to be from the presence of TSH receptors on thyroid cancer cells (1); however, non-TSH receptor-mediated growth is certainly a property of undifferentiated thyroid cancers.
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© 2006 Humana Press Inc., Totowa, NJ
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Wartofsky, L. (2006). Levothyroxine Therapy and Thyrotropin Suppression. In: Wartofsky, L., Van Nostrand, D. (eds) Thyroid Cancer. Humana Press. https://doi.org/10.1007/978-1-59259-995-0_29
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DOI: https://doi.org/10.1007/978-1-59259-995-0_29
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