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

Salman S Razvi; Helen Wild; Lorna Ingoe; Jonathan Vernazza; Mark Vanderpump; Simon H S Pearce; Marian Ludgate

doi:10.1210/clinem/dgae875

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

J Clin Endocrinol Metab. 2024 Dec 14:dgae875. doi: 10.1210/clinem/dgae875. Online ahead of print.

Authors

Salman S Razvi^{1

2}, Helen Wild², Lorna Ingoe², Jonathan Vernazza², Mark Vanderpump³, Simon H S Pearce¹, Marian Ludgate⁴

Affiliations

¹ Translational and Clinical Research Institute, Newcastle University Centre for Life, Central Parkway, Newcastle upon Tyne, NE1 3BZ, UK.
² Gateshead Health NHS Foundation Trust, Gateshead, NE9 6SX, UK.
³ OneWelbeck Endocrinology, Welbeck Street, Marylebone, London, UK.
⁴ Thyroid Research Group, Cardiff University School of Medicine, Cardiff, CF14 4XN, UK.

PMID: 39673773
DOI: 10.1210/clinem/dgae875

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.

Keywords: TSH; aging; thyroid function.