Iodine 123 thyroid scan image demonstrates a focus of increased activity at the right lower pole, with some suppression of the remainder of the gland.

Differential Diagnosis

•  Toxic hyperfunctioning adenoma (“hot nodule”): Significant radioiodine accumulation by the nodule and some suppression of uptake in the remainder of the gland make this the correct diagnosis.

•  Functioning adenoma (“warm nodule”): This will also have significant iodine accumulation but will not cause significant suppression of the remainder of the gland and is not typically toxic (does not cause hyperthyroidism).

•  Thyroid cancer: