Diagnosis of Levothyroxine Pseudo-malabsorption: The Results of Standardised Testing Protocol

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Sözen M., Canturk Z., Cetinarslan B., Tarkun I., Gezer E., Selek A.

JCPSP-JOURNAL OF THE COLLEGE OF PHYSICIANS AND SURGEONS PAKISTAN, no.9, pp.1099-1101, 2021 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Publication Date: 2021
  • Doi Number: 10.29271/jcpsp.2021.09.1099
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, CAB Abstracts, EMBASE, MEDLINE, Veterinary Science Database
  • Page Numbers: pp.1099-1101
  • Keywords: Levothyroxine absorption test, Pseudo-malabsorption, Resistant hypothyroidism, HYPOTHYROIDISM, ABSORPTION
  • Kocaeli University Affiliated: Yes


The levothyroxine absorption test for the assessment of pseudo-malabsorption in patients with refractory hypothyroidism has not been standardised. The aim of this observational study was to describe a protocol for levothyroxine (LT-4) absorption test in patients with refractory hypothyroidism, to report possible side effects and to emphasise the importance of pseudo-malabsorption in the differential diagnosis. The results of 10 patients, who underwent LT-4 absorption tests because thyroid stimulating hormone suppression could not be achieved despite the need for LT-4 > 3 mcg/kg/day, were retrospectively analysed. When compared with basal free T4 (fT4), a statistically significant increase in fT4 was observed after the first hour (p=0.012). fT4 reached its peak level and plateau at the 4(th) hour. The fT4 peak level increased 3.25 times compared to baseline. The shorter LT-4 absorption test with low doses may provide an alternative method to the commonly used longer protocols with higher doses to rule out malabsorption.