A single point mutation results in a over-functioning toxic nodule.
Autonomy occurs in some nodules in a goiter. When there is enough hormone production the TSH decreases and the FT4 may stay normal for years.This is subclinical hyperthyroidism that is associated with bone loss and atrial fibrillation ( rapid irregular heart beats), and increased cardiovascular mortality. DX of Toxic nodule requires low TSH high T4 and the presence of a nodule or nodular goiter.Increased radioiodine uptake in the nodule.
Image shows a thyroid scan of a toxic nodule with the DNA mutation shown below.