{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,28]],"date-time":"2026-01-28T01:12:10Z","timestamp":1769562730426,"version":"3.49.0"},"reference-count":24,"publisher":"Endocrinology Research Centre","issue":"6","license":[{"start":{"date-parts":[[2026,1,18]],"date-time":"2026-01-18T00:00:00Z","timestamp":1768694400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/www.probl-endojournals.ru\/jour\/about\/editorialPolicies#openAccessPolicy"}],"content-domain":{"domain":["www.probl-endojournals.ru"],"crossmark-restriction":true},"short-container-title":["Probl Endokrinol (Mosk)"],"abstract":"<jats:p>\n                    <jats:bold>BACKGROUND:<\/jats:bold>\n                    Thyroid hormone replacement therapy results remain unsatisfactory in 30-50% of cases. To differentiate between true levothyroxine sodium malabsorption and pseudomalabsorption due to poor compliance, several absorption assessment tests with different evaluation criteria are proposed.\n                  <\/jats:p>\n                  <jats:p>\n                    <jats:bold>AIM:<\/jats:bold>\n                    To determine the criteria for normal absorption of levothyroxine sodium when performing an oral test with a single bolus dose of 600 m\u0441g.\n                  <\/jats:p>\n                  <jats:p>\n                    <jats:bold>MATERIALS AND METHODS:<\/jats:bold>\n                    The study involved 20 healthy volunteers of both sexes, aged 18 to 35 years, with normal body weight. The bolus dose of levothyroxine sodium was 600 m\u0441g. Blood samples for determination of free thyroxine (fT4) concentration in serum were taken on an empty stomach, 1 hour, 2, 3, 4, 6 hours after taking the drug.\n                  <\/jats:p>\n                  <jats:p>\n                    <jats:bold>RESULTS:<\/jats:bold>\n                    After taking levothyroxine sodium at a dose of 600 mcg, the maximum level of free T4 was observed after 2 hours \u2014 21,00 pmol\/l [19,20; 23,16]. The minimum increase in the concentration of free T4 2 hours after taking levothyroxine sodium at a dose of 600 mcg was \u2014 18,0%, the maximum \u2014 91,1%.\n                  <\/jats:p>\n                  <jats:p>\n                    <jats:bold>CONCLUSION:<\/jats:bold>\n                    To assess the absorption of levothyroxine sodium, a single oral dose of 600 mcg of levothyroxine sodium is recommended. Absorption of levothyroxine sodium can be considered normal if the increase in free T4 concentration 2, 3, or 4 hours after the bolus dose is at least 18%.\n                  <\/jats:p>","DOI":"10.14341\/probl13665","type":"journal-article","created":{"date-parts":[[2026,1,27]],"date-time":"2026-01-27T12:17:04Z","timestamp":1769516224000},"page":"15-21","update-policy":"https:\/\/doi.org\/10.14341\/crossmarkpolicy2018","source":"Crossref","is-referenced-by-count":0,"title":["Evaluation of sodium levothyroxine absorption in real clinical practice using a single-bolus oral test"],"prefix":"10.14341","volume":"71","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8520-8702","authenticated-orcid":true,"given":"E. A.","family":"Troshina","sequence":"first","affiliation":[{"name":"Endocrinology Research Centre"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8077-9381","authenticated-orcid":true,"given":"N. V.","family":"Mazurina","sequence":"additional","affiliation":[{"name":"Endocrinology Research Centre"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0007-0651-3615","authenticated-orcid":true,"given":"M. H.","family":"Botasheva","sequence":"additional","affiliation":[{"name":"Endocrinology Research Centre"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6388-1544","authenticated-orcid":true,"given":"N. M.","family":"Platonova","sequence":"additional","affiliation":[{"name":"Endocrinology Research Centre"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9462-8522","authenticated-orcid":true,"given":"A. P.","family":"Pershina-Milyutina","sequence":"additional","affiliation":[{"name":"Endocrinology Research Centre"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0001-9129-9620","authenticated-orcid":true,"given":"I. R.","family":"Gasymova","sequence":"additional","affiliation":[{"name":"Endocrinology Research Centre"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"5458","published-online":{"date-parts":[[2026,1,18]]},"reference":[{"key":"ref1","doi-asserted-by":"crossref","unstructured":"Biruykova EV, Kileinikov DV, Solovieva IV. Hipothyreos: sovremennoye sostoyanie problemy. Meditsinskiy sovet. 2020;7:96-107. doi: https:\/\/doi.org\/10.21518\/2079-701X-2020-7-96-107","DOI":"10.21518\/2079-701X-2020-7-96-107"},{"key":"ref2","doi-asserted-by":"crossref","unstructured":"Manuiylova YA, Morgunova TB, Fadeev VV. Prichiny neeffektivnosty zamestitelnoiy terapii pervichnogo hipothyreosa. Klinicheskaya i experimentalnaya thireoidologiya. 2019;15(1):12-18. doi: https:\/\/doi.org\/10.14341\/ket10163","DOI":"10.14341\/ket10163"},{"key":"ref3","unstructured":"Petunina NA, Martirosyan NS, Telnova ME, i dr. Terapiya hypothyreosa v osobych gruppah patsientov. Effectivnaya pharmakotherapiya. 2021;17(20):38-41. doi: https:\/\/doi.org\/10.33978\/2307-3586-2021-17-20-38-41"},{"key":"ref4","doi-asserted-by":"crossref","unstructured":"Eligar V, Taylor PN, Okosieme OE, Leese GP, Dayan CM. Thyroxine replacement: a clinical endocrinologist\u2019s viewpoint. Ann Clin Biochem. 2016;53(Pt4):421-33. doi: https:\/\/doi.org\/10.1177\/0004563216642255","DOI":"10.1177\/0004563216642255"},{"key":"ref5","doi-asserted-by":"crossref","unstructured":"Caron P, Grunenwald S, Persani L, Borson-Chazot F, Leroy R, Duntas L. Factors influencing the levothyroxine dose in the hormone replacement therapy of primary hypothyroidism in adults. Rev Endocr Metab Disord. 2022;23(3):463-483. doi: https:\/\/doi.org\/10.1007\/s11154-021-09691-9","DOI":"10.1007\/s11154-021-09691-9"},{"key":"ref6","doi-asserted-by":"crossref","unstructured":"Colucci P, Yue CS, Ducharme M, Benvenga S. A Review of the Pharmacokinetics of Levothyroxine for the Treatment of Hypothyroidism. Eur Endocrinol. 2013;9(1):40-47. doi: https:\/\/doi.org\/10.17925\/EE.2013.09.01.40","DOI":"10.17925\/EE.2013.09.01.40"},{"key":"ref7","doi-asserted-by":"crossref","unstructured":"Skelin M, et al. Factors Affecting Gastrointestinal Absorption of Levothyroxine: A Review. Clin Ther. 2017;39(2):378-403. doi: https:\/\/doi.org\/10.1016\/j.clinthera.2017.01.005","DOI":"10.1016\/j.clinthera.2017.01.005"},{"key":"ref8","doi-asserted-by":"crossref","unstructured":"Canaris GJ, Manowitz NR, Mayor G, Ridgway EC. The Colorado thyroid disease prevalence study. Arch Intern Med. 2000;160(4):526-34. doi: https:\/\/doi.org\/10.1001\/archinte.160.4.526","DOI":"10.1001\/archinte.160.4.526"},{"key":"ref9","doi-asserted-by":"crossref","unstructured":"Somwaru LL, Arnold AM, Joshi N, Fried LP, Cappola AR. High frequency of and factors associated with thyroid hormone over-replacement and under-replacement in men and women aged 65 and over. J Clin Endocrinol Metab. 2009;94(4):1342-5. doi: https:\/\/doi.org\/10.1210\/jc.2008-1696","DOI":"10.1210\/jc.2008-1696"},{"key":"ref10","doi-asserted-by":"crossref","unstructured":"Caron P, Tudor C, Grunenwald S. Levothyroxine Absorption Test With the Daily Levothyroxine Dose in Patients With \u00abRefractory Hypothyroidism\u00bb. J Endocr Soc. 2025; 9(4):bvaf017. doi: https:\/\/doi.org\/10.1210\/jendso\/bvaf017","DOI":"10.1210\/jendso\/bvaf017"},{"key":"ref11","doi-asserted-by":"crossref","unstructured":"Gonzales KM, Stan MN, Morris JC, et al. The Levothyroxine Absorption Test: A Four-Year Experience (2015-2018) at The Mayo Clinic. Thyroid. 2019;29:1734-1742. doi: https:\/\/doi.org\/10.1089\/thy.2019.0256","DOI":"10.1089\/thy.2019.0256"},{"key":"ref12","doi-asserted-by":"crossref","unstructured":"Sun GE, Pantalone KM, Faiman C, et al. The clinical utility of free thyroxine in oral levothyroxine absorption testing. Endocr Pract. 2014;20:925-929. doi: https:\/\/doi.org\/10.4158\/EP13487.OR","DOI":"10.4158\/EP13487.OR"},{"key":"ref13","doi-asserted-by":"crossref","unstructured":"Yildirim Simsir I, Soyaltin UE, Ozgen AG. Levothyroxine absorption test results in patients with TSH elevation resistant to treatment. Endocrine. 2019;64:118-121. doi: https:\/\/doi.org\/10.1007\/s12020-019-01889-x","DOI":"10.1007\/s12020-019-01889-x"},{"key":"ref14","doi-asserted-by":"crossref","unstructured":"Ghosh S, Pramanik S, Biswas K, et al. Levothyroxine Absorption Test to Differentiate Pseudomalabsorption from True Malabsorption. Eur Thyroid J. 2020;9:19-24. doi: https:\/\/doi.org\/10.1159\/000504218","DOI":"10.1159\/000504218"},{"key":"ref15","doi-asserted-by":"crossref","unstructured":"Subramaniam K, Babu T, Sreevalsan KC, et al. Levothyroxine Absorption Test \u2013 Results and Follow Up of Patients from a Single Center. Indian J Endocrinol Metab. 2023;27:32-36. doi: https:\/\/doi.org\/10.4103\/ijem.ijem_188_21","DOI":"10.4103\/ijem.ijem_188_21"},{"key":"ref16","doi-asserted-by":"crossref","unstructured":"Balla M, Jhingan RM, Rubin DJ. Rapid levothyroxine absorption testing: a case series of nonadherent patients. Int J Endocrinol Metab. 2015;13(4):e31051. doi: https:\/\/doi.org\/10.5812\/ijem.31051","DOI":"10.5812\/ijem.31051"},{"key":"ref17","doi-asserted-by":"crossref","unstructured":"Van Wilder N, Bravenboer B, Herremans S, Vanderbruggen N, Velkeniers B. Pseudomalabsorption of levothyroxine: a challenge for the endocrinologist in the treatment of hypothyroidism. Eur Thyroid J. 2017;6(1):52-56. doi: https:\/\/doi.org\/10.1159\/000452489","DOI":"10.1159\/000452489"},{"key":"ref18","doi-asserted-by":"crossref","unstructured":"Lewandowski KC, Da\u0328browska K, Basin\u0301ska-Lewandowska M, Bolanowski M, Rucha\u0142a M, Lewin\u0301ski A. Adequate timing and constant supervision are the keys for successful implementation of levothyroxine or levothyroxine\/paracetamol absorption test. Thyroid Res. 2020;13:5. doi: https:\/\/doi.org\/10.1186\/s13044-020-00079-6","DOI":"10.1186\/s13044-020-00079-6"},{"key":"ref19","unstructured":"FDA. US Department of Health and Human Services, Food and Drug Administration. December 2000. Guidance for industry levothyroxine sodium tablets\u2014in vivo pharmacokinetic and bioavailability studies and in vitro dissolution testing. Center for Drug Evaluation and Research; 2016. Accessed October 15, 2022"},{"key":"ref20","unstructured":"Marina M, Ceda GP, Aloe R, Gnocchi C, Ceresini G. Circulating concentrations of free thyroxine after an oral intake of liquid LT4 taken either during fasting conditions or at breakfast. Acta Biomed. 2016;87(3):247-252"},{"key":"ref21","doi-asserted-by":"crossref","unstructured":"Walker JN, Shillo P, Ibbotson V, Vincent A, Karavitaki N, Weetman AP, et al. A thyroxine absorption test followed by weekly thyroxine administration: a method to assess nonadherence to treatment. Eur J Endocrinol. 2013;168:913\u20137. doi: https:\/\/doi.org\/10.1530\/EJE-12-1035","DOI":"10.1530\/EJE-12-1035"},{"key":"ref22","doi-asserted-by":"crossref","unstructured":"Dutta D, Jindal R, Kumar M, Mehta D, Dhall A, Sharma M. Efficacy and Safety of Once Weekly Thyroxine as Compared to Daily Thyroxine in Managing Primary Hypothyroidism: A Systematic Review and Meta-Analysis. Indian J Endocrinol Metab. 2021; 25(2):76-85. doi: https:\/\/doi.org\/10.4103\/ijem.IJEM_789_20","DOI":"10.4103\/ijem.IJEM_789_20"},{"key":"ref23","doi-asserted-by":"crossref","unstructured":"Oueslati I, Terzi A, Yazidi M, Kamoun E, Feki M, Chihaoui M. Levothyroxine absorption test in patients with refractory hypothyroidism: how to interpret patient\u2019s response to the test? Endocrine. 2025. doi: https:\/\/doi.org\/10.1007\/s12020-025-04312-w","DOI":"10.1007\/s12020-025-04312-w"},{"key":"ref24","doi-asserted-by":"crossref","unstructured":"Amiyangoda G, Antonypillai CN, Gunatilake SSC, Weerathunge TT, Ediriweera D, et al. Rapid supervised levothyroxine absorption test in refractory hypothyroidism: suggestion for assessing absorption using two blood samples in low-resource settings. Endocr Connect. 2024;13(10):e240277. doi: https:\/\/doi.org\/10.1530\/EC-24-0277","DOI":"10.1530\/EC-24-0277"}],"container-title":["Problems of Endocrinology"],"original-title":[],"link":[{"URL":"https:\/\/www.probl-endojournals.ru\/jour\/article\/viewFile\/13665\/10933","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"}],"deposited":{"date-parts":[[2026,1,27]],"date-time":"2026-01-27T12:17:22Z","timestamp":1769516242000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.probl-endojournals.ru\/jour\/article\/view\/13665"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,1,18]]},"references-count":24,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2026,1,18]]}},"URL":"https:\/\/doi.org\/10.14341\/probl13665","relation":{},"ISSN":["2308-1430","0375-9660"],"issn-type":[{"value":"2308-1430","type":"electronic"},{"value":"0375-9660","type":"print"}],"subject":[],"published":{"date-parts":[[2026,1,18]]}}}