why is cold nodule more malignant even though it has lesser activity?
less differentiated so less activity
Look, the appearance of hot and cold on thyroid scan depends on the degree of normal function of thyroid.
If a nodule is well-differentiated it will produce hormones and behave like normal thyroid; so appear as hot nodules.
But if a nodule is un-differentiated and non-functional, it will appear as cold in thyroid scan - and as it doesn’t resemble normal tissue (or lost it’s normal function), it’s more likely to be malignant.
Cause Cold war results in more damage