New Standards for Thyroid Function Testing May Alter Disease Classification

Recent research indicates that incorporating age, sex, and race-specific standards in thyroid function diagnostic tests could significantly impact the classification of thyroid diseases. This groundbreaking study highlights how many individuals currently diagnosed with thyroid disorders, particularly those with subclinical conditions, may actually have normal thyroid function when assessed with these tailored reference intervals.

Published in the Annals of Internal Medicine, this study is the first of its kind to analyze the implications of personalized reference intervals on thyroid disease diagnostics. Researchers from Shandong First Medical University in China conducted a cross-sectional analysis utilizing data from the National Health and Nutrition Examination Survey (NHANES) alongside information from a Chinese health database.

The study involved a representative sample of adults aged 20 and older from the U.S. and adults aged 18 and older from China. By examining variations in thyroid function tests across different demographic groups, the researchers established new diagnostic reference intervals that take into account age, sex, and race.

Findings from the study revealed that as age increases, there is a notable rise in the 97.5th percentile levels of thyroid-stimulating hormone (TSH), which serves as a key indicator of thyroid function. Conversely, total triiodothyronine (TT3) levels were observed to decline with age, while total thyroxine (TT4) levels remained stable. Additionally, it was found that women exhibited higher TT4 levels, whereas white participants had elevated TSH levels.

Utilizing the newly established reference intervals, researchers reclassified approximately 48.5% of individuals previously diagnosed with subclinical hypothyroidism as having normal thyroid function. This reclassification was particularly evident among women and white participants. Furthermore, 31.2% of those diagnosed with subclinical hyperthyroidism were also reclassified to normal, predominantly affecting women, Black participants, and Hispanic participants. Similar trends were observed in the supplementary data sourced from the Chinese database.

The implications of these findings are substantial, suggesting that the adoption of age, sex, and race-specific reference intervals could lead to a more accurate understanding of thyroid disease prevalence and management. The researchers advocate for the establishment of a consensus on defining and managing thyroid disorders based on these new insights.

For more detailed insights, refer to the original publication: Thyroid Function Reference Intervals by Age, Sex, and Race: A Cross-Sectional Study.