Comprehensive Thyroid Assessment in a Prospective Japanese Cohort: Epidemiology, Determinants, and Ultrasonographic Reference Ranges
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Context
A comprehensive evaluation of thyroid disease and health through multimodal assessment is warranted.
Objective
To clarify the epidemiology and clinical significance of abnormal findings on thyroid examinations in the general population.
Design
Prospective cohort study conducted between April 1, 2016, and December 31, 2021.
Setting
Japanese adults undergoing health checkups at the Preemptive Medicine and Lifestyle Disease Research Center, Kyoto University Hospital.
Main Outcome Measures
All subjects underwent thyroid function tests, ultrasonography, and 18 F-fluorodeoxyglucose-positron emission tomography (FDG-PET); anti-thyroperoxidase antibody (TPOAb) titers were measured in a subset of subjects.
Results
In the original cohort of 4,407 subjects (2,643 males and 1,764 females), the prevalence of thyroid dysfunction, increased blood flow on ultrasonography, diffuse thyroid FDG uptake, and thyroid nodules was 5.81%, 2.45%, 3.43%, and 39.71%, respectively; all were more frequent in females. Among 2,420 subjects with TPOAb measurements, TPOAb positivity was 7.19% and was significantly associated with thyroid dysfunction only at titers ≥ 128 IU/mL. Multivariate analyses identified age, sex, and thyroid volume as major determinants of thyroid function. Using data from 1,840 subjects without any thyroid abnormalities, we established sex-specific reference ranges for thyroid dimensions and found their correlations with age and body size.
Conclusions
This cohort provides epidemiological and physiological insights into thyroid health by integrating findings from thyroid function tests, ultrasonography, FDG-PET, and TPOAb measurements in the general population. Furthermore, the present study highlights associations across abnormal findings, relationships within thyroid physiology, and clinical relevance of high-titer TPOAb.
