Hyperthyroidism due to Subacute Thyroiditis (Nucl)	

Fig. 25.2 Hyperthyroidism due to subacute thyroiditis. 99mTc pertechnetate images taken 20 minutes after injection. Using the colour scale 0–100% (blue – green – yellow – red – purple) the thyroid can be seen in green, at the same level as the vascular activity in the aorta and heart inferiorly. Uptake is much reduced below that in the salivary glands and mouth seen superiorly. Normally, thyroid uptake is greater than salivary gland uptake. In this case, with clinical hyperthyroidism, there is severe reduction of uptake due to the inflammation of the thyroid. Autoimmune thyroiditis is a great mimic of the range of thyroid scan abnormalities, from the Hashimoto goitre with inhomogeneous uptake to appearances of ‘warm’ or ‘cold’ defects, solitary or multiple, or asymmetric uptake.

See also:
• Autoimmune Thyroid Disease and Hashimoto's Thyroiditis