The Use of ^99mTc-Methoxy-isobutyl-isonitrile (sestaMIBI) Uptake on Scintigraphy (^99m-STS) in Amiodarone-Induced Thyrotoxicosis: Case Series and Review of the Literature

Table 2

Summary of clinical, biochemical, and radiological imaging differentiation between AIT-1 and AIT-2 [1–19].

Modalities	AIT-1	AIT-2
Underlying thyroid disease	Yes (Graves’ disease or MNG)	No
Time after starting amiodarone	Short (median 3 months)	Long (median 30 months)
Thyroid antibodies including TSI, TRAb, microsomal TPO antibodies	May be positive	Usually absent
RAIU	Low/normal/increased (uptake can be inhibited in high intrathyroidal iodine concentration and increased in iodine-deficient regions)	Low/absent
Circulating IL-6	Normal to high	Frequently marked elevated
T4/T3 ratio	Usually <4	Usually >4
Thyroid US	Diffuse or nodular goiter	Normal or small thyroid
CFDS	Increased	Absent
^99m-STS	Increased uptake in the thyroid in the initial images followed by washout in the delayed images	Absent uptake in the thyroid in the initial and delayed images