SFEBES2023 Poster Presentations Thyroid (63 abstracts)
Thyroid hormone profiles on non-standard thyroid hormone replacement
Peter Taylor 1 , Aneela Arooj 2 , Stephanie Hanna 1 , Vinay Eligar 1 , Zubair Muhammad 3 , Mike Stedman 4 , Lakdasa Premawardhana 1 , Onyebuchi Okosieme 1 , Adrian Heald 5 & Colin Dayan 1
1Cardiff University, Cardiff, United Kingdom. 2UHW, Cardiff, United Kingdom. 3Aberdeen Royal Infirmary, Aberdeen, United Kingdom. 4Res consortium, Manchester, United Kingdom. 5University of Manchester, Manchester, United Kingdom
Context: Approximately 10% of patients on levothyroxine remain symptomatic despite restoration of biochemical euthyroidism. Some therefore utilise alternatives to levothyroxine monotherapy including combination thyroid hormone replacement, T3 monotherapy and desiccated thyroid extract (DTE). We examined thyroid hormone profiles in these patients.
Methods: We examined 49 individuals 14 on combination thyroid hormone replacement,14 on T3 monotherapy and 21 on DTE). Hourly blood tests (TSH, T3 and T4) were undertaken between 8.30am-4.30pm. Area under the curve (AUC) analysis was performed and odds of having a very low TSH (<0.05mU/l) and completely suppressed TSH (<0.02mU/l) at 08:30 were undertaken with adjustment for age.
Results: The highest T3 levels were seen with T3 monotherapy. Combined T3 and T4 dose, T3 dose and T4 dose were not associated with increased odds of a very low or a completely suppressed TSH. T3 monotherapy and DTE had higher AUCT3 levels and lower AUCT4 levels than combination thyroid hormone replacement. AUCT3 was associated with increased odds of very low TSH OR=2.95 (95%CI 1.45, 6.03) P=0.003 and a completely suppressed TSH OR=2.21 (95%CI 1.12, 4.38) P=0.02. Maximum T3 was associated with increased odds of very low TSH OR=2.51 (95%CI 1.24, 5.05) P=0.01 and completely suppressed TSH OR=2.31 (95%CI 1.13, 4.70) P=0.02. Any T3 level above 7.0 pmol/l was associated with increased odds of a very low TSH OR=11.7 (95%CI 1.23, 111) P=0.03. No association was seen with AUCT4 or maximum T4 level.
Discussion: T3 levels have a greater negative impact on TSH levels than T4 levels. Notably peak T3 levels have a substantial impact and appear to be more important in influencing TSH levels than total T3 dose. Taken together this suggests that strategies to reduce peak T3, such as slow release T3, should be investigated as a path to enabling moderate T3 doses without substantially suppressing TSH.
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Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
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