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Journal of Thyroid Research
Volume 2019, Article ID 4106816, 8 pages
https://doi.org/10.1155/2019/4106816
Review Article

Challenges in Interpreting Thyroid Stimulating Hormone Results in the Diagnosis of Thyroid Dysfunction

1Institute of Genetic Medicine, Newcastle University, Newcastle-upon-Tyne NE1 3BZ, UK
2Department of Internal Medicine, Division of Endocrinology and Diabetes, University of the Witwatersrand, Johannesburg, South Africa
3Medical Affairs EMEA, Merck Serono Middle East FZ-LLC, Dubai, UAE

Correspondence should be addressed to Salman Razvi; ku.ca.lcn@ivzar.namlas

Received 31 July 2019; Accepted 1 September 2019; Published 22 September 2019

Academic Editor: Noriyuki Koibuchi

Copyright © 2019 Salman Razvi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The pituitary hormone, thyrotropin (TSH), is regarded as the primary biomarker for evaluating thyroid function and is useful in guiding treatment with levothyroxine for patients with hypothyroidism. The amplified response of TSH to slight changes in thyroid hormone levels provides a large and easily measured signal in the routine care setting. Laboratories provide reference ranges with upper and lower cutoffs for TSH to define normal thyroid function. The upper limit of the range, used to diagnose subclinical (mild) hypothyroidism, is itself a matter for debate, with authoritative guidelines recommending treatment to within the lower half of the range. Concomitant diseases, medications, supplements, age, gender, ethnicity, iodine status, time of day, time of year, autoantibodies, heterophilic antibodies, smoking, and other factors influence the level of TSH, or the performance of current TSH assays. The long-term prognostic implications of small deviations of TSH from the reference range are unclear. Correction of TSH to within the reference range does not always bring thyroid and other biomarkers into range and will not always resolve the patient’s symptoms. Overt hypothyroidism requires intervention with levothyroxine. It remains important that physicians managing a patient with symptoms suggestive of thyroid disease consider all of the patient’s relevant disease, lifestyle, and other factors before intervening on the basis of a marginally raised TSH level alone. Finally, these limitations of TSH testing mitigate against screening the population for the undoubtedly substantial prevalence of undiagnosed thyroid disease, until appropriately designed randomised trials have quantified the benefits and harms from this approach.