SFEBES2022 Poster Presentations Thyroid (41 abstracts)
Comparison of supervised rapid thyroxine absorption test in refractory and well-controlled primary hypothyroid patients in a tertiary care center in Sri Lanka and formulation of a prediction model to predict the expected FT4 rise during the test
C G K Amiyangoda 1,2 , C N Antonypillai 3 , S S C G Gunatilake 3 , D Ediriweera 4 , S G P D Kosgollana 3 , R D P Jayawardena 5 , H A N D Thissera 5 , W J Emalka 1 & H U Deraniyagala 6
1Faculty of Medicine, University of Peradeniya, Peradeniya, Sri Lanka; 2Oxford Centre for Diabetes Endocrinology and Metabolism, Churchill Hospital, Oxford, United Kingdom; 3Diabetes and Endocinology Unit, National Hospital, Kandy, Sri Lanka; 4Health Data Science Unit, Faculty of Medicine, University of Kelaniya, Kelaniya, Sri Lanka; 5Department of Biochemistry, National Hospital, Kandy, Sri Lanka; 6Faculty of Medicine, University of Peradeniya, Peradeniya, Sri Lanka
Introduction: Refractory hypothyroidism is associated with significantly increased morbidity and healthcare costs. During the evaluation of refractory disease, a thyroxine absorption test is frequently performed using different protocols. We assessed the usefulness of the supervised rapid thyroxine absorption test in a low-resource setting and formulated a useful model to determine the expected FT4 rise in hypothyroid patients without known malabsorption.
Methods: A cross-sectional study was performed comparing 24 cases of refractory hypothyroidism (TSH > 4 mIU/l on thyroxine >2 micrograms/kg/day) without known malabsorption and 25 controls (normal TSH on thyroxine <1.6 micrograms/kg/day). Data on baseline characteristics and medication history were collected. A supervised rapid thyroxine absorption test was performed in both groups giving oral levothyroxine 1000 micrograms after 10 hours fast. Serum TSH at baseline (0 hours) and FT4 at 0,1,2,3,4,5 hours following thyroxine ingestion were analyzed.
Results: There was no statistically significant difference in FT4 levels during absorption test in both groups. Males had a higher thyroxine absorption rate than females (P= value = 0.0136). Higher baseline TSH was associated with reduced absorption rate. (P value –=0.0002). After pooling all absorption tests of both groups, it showed a gradual FT4 rise until 4 hours and plateaued thereafter.
Mean FT4 rise from the baseline (95% CI):
| Hours after thyroxine ingestion | Mean percentage rise from the baseline (0 hours) | 95% CI |
| 1 | 52.1% | 40.2% - 64% |
| 2 | 104.3% | 88.0% - 121% |
| 3 | 149.4% | 128.4% - 170.5% |
| 4 | 152.7% | 136.7% - 177.7% |
| 5 | 156.9% | 133.8% - 180.0% |
Conclusion: There was no statistically significant difference in thyroxine absorption in refractory and well-controlled hypothyroid patients in this cohort. The new model would be useful in a low-resource setting where, measurement of FT4 only at 0 and 4 hours and calculating the percentage rise of FT4, can be used to exclude pseudo-malabsorption in refractory hypothyroidism.
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Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
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