Reevaluation of L-Thyroxine Dosage (1986)

Letters and Corrections1 November 1986Reevaluation of L-Thyroxine DosageMITCHELL A. LAZAR, M.D., Ph.D.MITCHELL A. LAZAR, M.D., Ph.D.Search for more papers by this authorAuthor, Article, and Disclosure Informationhttps://doi.org/10.7326/0003-4819-105-5-797 SectionsAboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail ExcerptTo the editor: The findings reported by Hennessey and colleagues (1) in the July issue are not new, and the conclusions presented are simplistic and misleading. Ingbar and coworkers (2), Pearce and Himsworth (3), and Rendell and Salmon (4) have previously noted that many patients receiving "therapeutic doses" of oralL-thyroxine had serum thyroxine levels that were above the normal range for patients not taking a thyroxine preparation. Often, serum levels of triiodothyronine were within the normal range and correlated better with clinical status as assessed by symptoms and signs of hyperthyroidism than did the thyroxine levels. Hennessey and colleagues...References1. HENNESSEYEVAULTSENGBURMANWARTOFSKY JJYKL. L-Thyroxine dosage: a reevaluation of therapy with contemporary preparations. Ann Intern Med. 1986;105:11-5. LinkGoogle Scholar2. INGBARBORGESIFLAHKLEINMANNBRAVERMANINGBAR JMSRLS. Evaluating serum thyroxine concentration in patients receiving "replacement" doses of levothyroxine. J Endocrinol Invest. 1982;5:77-85. CrossrefMedlineGoogle Scholar3. PEARCEHIMSWORTH CR. Total and free thyroid hormone concentrations in patients receiving maintenance replacement treatment with thyroxine. Br Med J. 1984;288:693-5. CrossrefMedlineGoogle Scholar4. RENDELLSALMON MD. "Chemical hyperthyroidism": the significance of elevated serum thyroxine levels in L-thyroxine treated individuals. Clin Endocrinol. 1985;22:693-700. CrossrefMedlineGoogle Scholar5. JENNINGSO'MALLEYGRIFFINNORTHOVERROSENTHAL PBKBF. Relevance of increased serum thyroxine concentrations associated with normal serum triiodothyronine values in hypothyroid patients receiving thyroxine: a case for "tissue thyrotoxicosis. " Br Med J. 1984;289:1645-7. CrossrefMedlineGoogle Scholar6. LARSENSILVAKAPLAN PJM. Relationships between circulating and intracellular thyroid hormones: physiological and clinical implications. Endocrinol Rev. 1981;2:87-102. CrossrefMedlineGoogle Scholar7. VAN DOORNROELFSEMAVAN DER HEIDE JFD. Concentrations of thyroxine and 3,5,3'-triiodothyronine at 34 different sites in euthyroid rats as determined by an isotopic equilibrium technique. Endocrinology. 1985;117:1201-8. CrossrefMedlineGoogle Scholar1. JENNINGSO'MALLEYGRIFFINNORTHOVERROSENTHAL PBKBF. Relevance of increased serum thyroxine concentrations associated with normal serum triiodothyronine values in hypothyroid patients receiving thyroxine: a case for "tissue thyrotoxicosis. " Br Med J. 1984;289:1645-7. CrossrefMedlineGoogle Scholar2. INGBARBORGESIFLAHKLEINMANNBRAVERMANINGBAR JMSRLS. Evaluating serum thyroxine concentration in patients receiving "replacement" doses of levothyroxine. J Endocrinol Invest. 1982;5:77-85. CrossrefMedlineGoogle Scholar3. FISHSCHWARTZCAVANAUGHBANTLESTEFFESOPPENHEIMER LHJJMJ. Is serum T3 and not serum T4 the primary signal regulating the release of pituitary TSH in man [Abstract]? Clin Res. 1986;34:424A. Google Scholar1. HENNESSEYEVAULTSENGBURMANWARTOFSKY JJYKL. L-Thyroxine dosage: a reevaluation of therapy with contemporary preparations. Ann Intern Med. 1986;105:11-5. LinkGoogle Scholar2. WONGVOLPÉ MR. What is the best test for monitoring levothyroxine therapy? Can Med Assoc J. 1981;124:1181-3. MedlineGoogle Scholar This content is PDF only. To continue reading please click on the PDF icon. Author, Article, and Disclosure InformationAffiliations: Brigham and Women's Hospital Boston, MA 02115 PreviousarticleNextarticle Advertisement FiguresReferencesRelatedDetails Metrics Cited BySubclinical Hyperthyroidism: Possible Danger of Overzealous Thyroxine Replacement Therapy 1 November 1986Volume 105, Issue 5Page: 797-798KeywordsHyperthyroidismSigns and symptomsThyroxineTriiodothyronine Issue Published: 1 November 1986 PDF DownloadLoading ...