Changes in thyroid function and autoimmunity in older individuals: longitudinal analysis of the Whickham cohort

Razvi, Salman S., Wild, Helen, Ingoe, Lorna, Vernazza, Jonathan, Vanderpump, Mark, Pearce, Simon H. S. and Ludgate, Marian 2024. Changes in thyroid function and autoimmunity in older individuals: longitudinal analysis of the Whickham cohort. The Journal of Clinical Endocrinology & Metabolism 10.1210/clinem/dgae875

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Abstract

Background Longitudinal studies of thyroid function have demonstrated differing results. It remains unclear whether changes in thyroid function affect the diagnosis of subclinical thyroid dysfunction with ageing. Methods Survivors of the Whickham cohort study were evaluated on two occasions between the years 2008–2012 and 2016–2019. Serum thyrotropin (TSH), free thyroxine (FT4), free triiodothyronine (FT3) and thyroid peroxidase antibody (TPOAb) were measured on both occasions using the same assay under similar conditions. Individuals with known thyroid disease or on medications affecting thyroid function were excluded. Comorbidities were noted, functional mobility was assessed by the timed up-and-go test and muscle function was evaluated by the hand grip strength test. Results In 204 individuals (mean age 77.0 [±6.6] years, 114 [56%] female), followed over a median (IQR) of 7.8 (7.3–8.2) years, serum TSH increased by 0.29 mU/L (12.4%), FT3 and TPOAb reduced by 0.1 pmol/L (-2.1%) and 0.6 U/L (-11.2%) and there were no significant changes in FT4 levels. The calculated upper limit of serum TSH increased over the follow-up period from 4.74 mU/L to 6.28 mU/L. The relationship between serum TSH and FT4 at both time points were not significantly different. Utilising standard laboratory reference ranges, the prevalence of subclinical hypothyroidism increased from 3.5% at baseline to 9.0% at follow-up. However, adopting a visit-specific TSH reference range reduced the prevalence of subclinical hypothyroidism at both time points to 2.0%. Discussion Thyroid function demonstrates subtle but significant changes with age. Utilising standard reference ranges tends to increase the diagnosis of subclinical hypothyroidism in older euthyroid individuals. Our data suggest that adopting age-appropriate TSH reference ranges may reduce the risk of diagnosing and (potentially unnecessarily) treating subclinical hypothyroidism.

Item Type:	Article
Date Type:	Published Online
Status:	In Press
Schools:	Medicine
Additional Information:	License information from Publisher: LICENSE 1: URL: https://creativecommons.org/licenses/by/4.0/, Start Date: 2024-12-14
Publisher:	Oxford University Press
ISSN:	0021-972X
Date of First Compliant Deposit:	8 January 2025
Date of Acceptance:	12 December 2024
Last Modified:	08 Jan 2025 10:15
URI:	https://orca.cardiff.ac.uk/id/eprint/175096

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