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Lookup NU author(s): Dr Salman Razvi, Professor Simon PearceORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
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.
Author(s): Razvi SS, Wild H, Ingoe L, Vernazza J, Vanderpump M, Pearce SHS, Ludgate M
Publication type: Article
Publication status: Published
Journal: Journal of Clinical Endocrinology & Metabolism
Year: 2024
Pages: Epub ahead of print
Online publication date: 14/12/2024
Acceptance date: 13/12/2024
Date deposited: 13/12/2024
ISSN (print): 0021-972X
ISSN (electronic): 1945-7197
Publisher: Oxford University Press
URL: https://doi.org/10.1210/clinem/dgae875
DOI: 10.1210/clinem/dgae875
Data Access Statement: Some or all datasets generated during and/or analyzed during the current study are not publicly available but are available from the corresponding author on reasonable request.
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