Quantitative thyroid scintigraphy for the differentiation of Graves' disease and hyperthyroid autoimmune thyroiditis

Area of Science:

• Endocrinology
• Nuclear Medicine
• Thyroidology

Background:

• Global (99m)Tc-pertechnetate thyroid uptake under suppression (TCTUs) can estimate iodine clearance and is elevated in Graves' disease (GD).
• Decreased TCTUs have been noted in autoimmune thyroiditis (AIT), but systematic data in hyperthyroid AIT patients are limited.
• Differentiating between AIT and GD is crucial for appropriate hyperthyroidism management.

Purpose of the Study:

• To evaluate the utility of TCTUs in distinguishing between AIT and GD in patients presenting with hyperthyroidism.
• To provide systematically investigated data on TCTUs in a larger cohort of AIT patients with subclinical or overt hyperthyroidism.

Main Methods:

• TCTUs were measured in 59 untreated hyperthyroid GD patients and 51 hyperthyroid AIT patients.
• GD was diagnosed based on hyperthyroidism, decreased thyroid echogenicity, and elevated TSH-receptor autoantibodies (TRAb).
• AIT was defined by decreased thyroid echogenicity, absence of elevated TRAb, presence of anti-thyroid peroxidase (anti-TPO) antibodies, and spontaneous remission or subclinical hypothyroidism.

Main Results:

• Thyroid volumes were significantly smaller in AIT patients compared to GD patients.
• TRAb levels were markedly higher in GD patients than in AIT patients.
• TCTUs values were significantly lower in AIT patients (median: 0.9%) compared to GD patients (median: 5.7%).

Conclusions:

• Quantitative thyroid scintigraphy using (99m)TcO(4)(-) provides a rapid and reliable method for differentiating between hyperthyroid GD and AIT.
• TCTUs measurements can aid in the etiological diagnosis of hyperthyroidism.