ETA2023 45th Annual Meeting of the European Thyroid Association ETA 2023 Oral Session 8: Hypothyrodism / Nodules (5 abstracts)
Thyroid hormone profiles in individuals on non standard thyroid hormone replacement
Peter Taylor 1 , Aneela Arooj 2 , Stephanie Hanna 2 , Vinay Eligar 3 , Zubair Muhammed 4 , Mike Stedman 5 , Lakdasa Premawardhana 6 , Onyebuchi Okosieme 7 , Adrian Heald 8 & Colin Dayan 9
1Cardiff University, School of Medicine, Cardiff University School of Medicine, Cardiff, United Kingdom; 2Cardiff University; 3Imperial College London Diabetes Centre; 4Aberdeen Royal Infirmary; 5Res Consortium, United Kingdom; 6Yyf Hospital, University Hospital of Wales, Aneurin Bevan University Health Board, Cardiff, United Kingdom; 7Cardiff University, Prince Charles Hospital, Cardiff, United Kingdom; 8Salford Royal Hospital, Endocrinology, Salford, United Kingdom; 9Thyroid Research Group, School of Medicine, Cardiff University, Cardiff, United Kingdom
Context: Up to 15% of people with hypothyroidism remain symptomatic despite treatment with levothyroxine. A proportion of these utilise combination thyroid hormone replacement, T3 monotherapy and desiccated thyroid extract (DTE). We sought to explore thyroid hormone profiles in these patients.
Methods: We performed hourly blood tests (8.30am-4.30pm) to assess TSH, T3 and T4 levels in 49 individuals (n =14 combination thyroid hormone replacement, n =14 on T3 monotherapy and n =21 on DTE). 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: T3 monotherapy and DTE had higher AUCT3 levels and lower AUCT4 levels than combination thyroid hormone replacement. 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. 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. No association was seen with AUCT4 or maximum T4 level. Any T3 level above 7.0pmol/l was associated with increased odds of a very low TSH OR=11.7 (95%CI 1.23, 111) P = 0.03.
Discussion: T3 levels have a greater negative impact on TSH levels than T4 levels. This impedes maintenance of normal TSH levels in individuals on non standard thyroid hormone replacement. Notably the peak T3 levels observed during the day 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.
Volume 92
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Endocrine Abstracts
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