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Levothyroxine Absorption Test to Differentiate Pseudomalabsorption from True Malabsorption.


ABSTRACT: Background:The levothyroxine absorption test for evaluation of pseudomalabsorption in patients with primary hypothyroid is not standardised. An individual in whom a workup for malabsorption is warranted remains undefined. Methods:Twenty-five euthyroid, 25 newly diagnosed hypothyroid, 25 treated hypothyroid with normalised TSH, and 25 hypothyroid subjects with elevated TSH despite adequate dose of levothyroxine for more than 6 months, and 10 euthyroid subjects with true malabsorption were administered levothyroxine (10 ?g/kg or maximum 600 ?g) to study its absorption profile by measuring free T4 level at hourly intervals for 5 h. Results : Free T4 peaked at 3 h with marginal insignificant decline at 4 h in all groups. The increments of free T4 (between baseline and 3 h) of the four groups (except malabsorption) were not statistically different. The mean increment of free T4 in true malabsorption was 0.39 ng/dL (95% CI: 0.29-0.52) and it was 0.78 ng/dL (95% CI: 0.73-0.85) (10.4 pmol/L) for other groups combined together. The cut off of free T4 increment at 3 h from baseline above 0.40 ng/dL had a sensitivity of 97% and specificity of 80% (AUC 0.904, p < 0.001) to exclude true malabsorption. Conclusion:Subjects with elevated TSH on adequate dose of LT4 can be reliably diagnosed to be non-adherent to treatment with levothyroxine absorption test. The incremental value above 0.40 ng/dL (5.14 pmol/L) at 3 h may be useful to identify individuals where workup of malabsorption is unwarranted.

SUBMITTER: Ghosh S 

PROVIDER: S-EPMC7024890 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Levothyroxine Absorption Test to Differentiate Pseudomalabsorption from True Malabsorption.

Ghosh Sujoy S   Pramanik Subhodip S   Biswas Kaushik K   Bhattacharjee Kingshuk K   Sarkar Rajib R   Chowdhury Subhankar S   Mukhopadhyay Pradip P  

European thyroid journal 20191120 1


<h4>Background</h4>The levothyroxine absorption test for evaluation of pseudomalabsorption in patients with primary hypothyroid is not standardised. An individual in whom a workup for malabsorption is warranted remains undefined.<h4>Methods</h4>Twenty-five euthyroid, 25 newly diagnosed hypothyroid, 25 treated hypothyroid with normalised TSH, and 25 hypothyroid subjects with elevated TSH despite adequate dose of levothyroxine for more than 6 months, and 10 euthyroid subjects with true malabsorpti  ...[more]

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