Thyroid volumetric measurement and quantitative thyroid scintigraphy in dogs

Area of Science:

• Veterinary Nuclear Medicine
• Canine Endocrinology

Background:

• Thyroid abnormalities are common in dogs.
• Accurate assessment of thyroid function is crucial for diagnosis and treatment.

Purpose of the Study:

• To evaluate the utility of quantitative technetium-99m pertechnetate thyroid scintigraphy in differentiating euthyroid and hypothyroid canine patients.
• To compare thyroid size and radioiodine uptake between euthyroid and hypothyroid dogs.

Main Methods:

• Sixty-two dogs with suspected thyroid abnormalities underwent volumetric thyroid measurement and quantitative 99mTc-pertechnetate scintigraphy.
• Scintigraphic parameters included thyroid/salivary gland region of interest (ROI) ratio, thyroid/background ROI ratio, and 20-min thyroid radioactivity uptake.
• Statistical analysis was performed using Student's unpaired and paired tests.

Main Results:

• No significant difference in total thyroid size was observed between euthyroid (3.60 ± 1.36 cm3) and hypothyroid (n=36) dogs.
• Hypothyroid dogs showed significantly lower thyroid/salivary gland ROI ratios (1.08 ± 0.56 vs. 2.01 ± 0.55), thyroid/background ROI ratios (2.32 ± 0.70 vs. 3.86 ± 0.90), and 20-min thyroid radioactivity uptake (0.34 ± 0.22% I.D. vs. 1.17 ± 0.71% I.D.) compared to euthyroid dogs (p < 0.001).
• No significant inter-lobar differences in quantitative data were found in either group.

Conclusions:

• Quantitative scintigraphy, particularly radioiodine uptake, is a valuable tool for assessing thyroid function in dogs.
• Reduced radioiodine uptake is a sensitive indicator of hypothyroidism in canines, even when thyroid size is not significantly altered.