Diffusely Increased ¹⁸F-FDG Uptake in the Thyroid Gland and Risk of Thyroid Dysfunction: A Cohort Study

Area of Science:

• Nuclear Medicine
• Endocrinology
• Radiology

Background:

• The clinical significance of incidental diffuse thyroid uptake on 18F-FDG PET/CT scans is not well-established.
• Thyroid dysfunction poses a significant health burden, necessitating improved diagnostic approaches.

Purpose of the Study:

• To investigate the association between incidentally identified diffuse thyroid 18F-FDG uptake and the subsequent development of thyroid dysfunction.
• To determine the risk of prevalent and incident thyroid dysfunction in individuals with diffuse thyroid uptake.

Main Methods:

• A large cohort study of 39,098 Korean adults without prior malignancy or thyroid disease.
• Utilized 18F-FDG whole-body PET/CT scans and thyroid function tests (TSH, free thyroxine) at baseline.
• Employed a parametric proportional hazard model for up to 5 years of follow-up, analyzing incident hypothyroidism and hyperthyroidism.

Main Results:

• Diffuse thyroid 18F-FDG uptake was significantly associated with an increased risk of both prevalent and incident thyroid dysfunction.
• The multivariable-adjusted hazard ratios for incident hypothyroidism and hyperthyroidism were 15.72 and 7.38, respectively, in individuals with diffuse uptake compared to those without.
• The study identified 102 incident hypothyroidism and 172 incident hyperthyroidism cases over 104,261.4 person-years of follow-up.

Conclusions:

• Incidental diffuse thyroid uptake on 18F-FDG PET/CT scans is a significant predictor of increased risk for thyroid dysfunction.
• Routine baseline and follow-up thyroid evaluations are recommended for individuals exhibiting diffuse thyroid uptake on PET/CT scans.
• This finding aids in identifying at-risk individuals and facilitates timely management of thyroid dysfunction.