Serum thyroid stimulating hormone level for predicting utility of thyroid uptake and scan

Area of Science:

• Endocrinology
• Nuclear Medicine
• Diagnostic Imaging

Background:

• Thyroid uptake and scan (TUS) aids in differentiating thyrotoxicosis causes.
• Current guidelines suggest TUS for low thyroid-stimulating hormone (TSH) but lack a specific TSH threshold.
• This ambiguity can lead to unnecessary diagnostic procedures.

Purpose of the Study:

• To establish a TSH cutoff value for optimizing the diagnostic utility of TUS.
• To identify a threshold that maximizes the likelihood of determining thyrotoxicosis etiology via TUS.
• To reduce unnecessary testing and associated burdens.

Main Methods:

• Retrospective analysis of 137 patients undergoing TUS for low TSH (<0.4 μU/mL).
• Receiver operating characteristic (ROC) curve analysis to determine optimal TSH cutoff.
• Evaluation of TUS diagnostic yield and specific etiological diagnoses.

Main Results:

• TUS yielded a diagnosis in 90% of cases; 10% were inconclusive.
• Common diagnoses included Graves' disease (52%), toxic multinodular goiter (19%), and thyroiditis (12%).
• Optimal TSH cutoff was ≤0.02 μU/mL (sensitivity 80%, specificity 93%), with a ROC AUC of 0.86.

Conclusions:

• TSH levels effectively predict the diagnostic yield of TUS for thyrotoxicosis.
• A TSH cutoff of ≤0.02 μU/mL indicates a high likelihood of TUS diagnostic utility.
• This finding supports judicious TUS use, minimizing costs and patient inconvenience.