Stability of thyroid function in older adults: The Birmingham Elderly Thyroid Study

Lesley Roberts, Deborah McCahon, Oliver Johnson, M. Sayeed Haque, James Parle, F. D.Richard Hobbs*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

6 Citations (Scopus)
115 Downloads (Pure)

Abstract

Background: Thyroid function tests (TFT) are among the most requested tests internationally. Testing practice is however inconsistent and potentially sub-optimal and overly costly. The natural history of thyroid function remains poorly understood.

Aim: To establish the stability of thyroid function over time, and identify predictors of development of overt thyroid dysfunction
Design: Longitudinal follow-up

Setting: 19 general practices, UK

Method: 2936 Birmingham Elderly Thyroid Study (BETS I) with a baseline TFT result indicating euthyroid or subclinical state were re-tested after approximately 5 years. Change in TSH, FT4 and thyroid status between baseline, and follow-up was determined. Predictors of progression to overt dysfunction were modelled.

Results: Participants contributed 12,919-person years, 17 cases of overt thyroid dysfunction were identified, 13 having been classified at baseline as euthyroid and four as having subclinical thyroid dysfunction. Individuals with subclinical results at baseline were 10 and 16-fold more likely to develop overt hypo and hyperthyroidism respectively compared with euthyroid individuals. TSH and FT4 demonstrated significant stability over time with 61% of participants having a repeat TSH concentration within 0.5 mIU/L of their original result. Predictors of overt hypothyroidism included new treatment with amiodarone (OR 92.1), a new diagnosis of atrial fibrillation (OR 7.4), or renal disease (OR 4.8).

Conclusion: High stability of thyroid function demonstrated over the 5-year interval period should discourage repeat testing, especially where a euthyroid result is in the recent clinical record. Reduced repeat TFTs in older individuals is possible without conferring risk and could result in significant cost savings.
Original languageEnglish
Pages (from-to)e718-e726
Number of pages9
JournalBritish Journal of General Practice
Volume68
Issue number675
Early online date28 Jul 2018
DOIs
Publication statusPublished - 1 Oct 2018

Keywords

  • Ageing
  • General practice
  • Primary health care
  • Subclinical thyroid dysfunction
  • Symptoms
  • Thyroid function test

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