McCahon, Deborah (2012)
Ph.D. thesis, University of Birmingham.
Subclinical thyroid dysfunction (SCTD), characterised by abnormal serum thyrotrophin concentrations (TSH) with normal free thyroxine (FT\(_4\)), is regularly encountered in primary care. The clinical manifestations of SCTD are not well established, particularly in older individuals in whom SCTD, co-morbid conditions and symptoms frequently occur. This thesis clarifies the clinical expression and pathophysiological consequences of SCTD in the elderly with reference to existing evidence and a cross-sectional study evaluating thyroid function (TF), health status and specific symptoms in community dwelling individuals aged 65 years and above. TF for 2870 participants was categorised, 2703 (94%) euthyroid, 138 (4.8%) subclinical hypothyroidism and 29 (1%) subclinical hyperthyroidism. No significant differences in the prevalence of individual symptoms, pairs of symptoms or multiple symptoms were observed between TF groups. In the presence of individual or multiple symptoms, health status scores were significantly lower. In conclusion, symptoms and impaired health status were not associated with SCTD in this study. Results suggest that assessment of symptoms and health status does not aid clinical decision making with respect to management of SCTD in the elderly. Coupled with weak evidence demonstrating pathophysiological consequences in SCTD, overall findings suggest this population is unlikely to benefit from treatment for SCTD.
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