Ask the Doctor Hot or Cold Nodule
While there is still disagreement regarding the initial evaluation of a thyroid nodule, the majority of endocrinologists begin with a fine-needle aspiration (biopsy) unless the thyroid blood tests indicate hyperthyroidism (a low TSH). Patients who have a low TSH associated with a nodule are more likely to have an autonomous "hot" nodule. Since autonomous nodules are "never" malignant, a biopsy is not needed.
A thyroid scan is needed to diagnosis an autonomous nodule in a patient with a low TSH. Occasionally a technectiun scan will give false results because some malignancies can concentrate technectium, giving the picture of a "hot" nodule. Nodules that appear "hot" on a radioiodine scan are virtually never malignant (there have been very rare exceptions). Therefore, if you have a radioiodine scan which shows your nodule to be autonomous ("hot"), a biopsy is not necessary. Thyroid hormone suppression is logically used for non-cold nodules, since the goal of suppression of thyroid hormone therapy is to reduce the TSH and most patients with autonomous nodules already have low TSH levels.
If a nodule shrinks on thyroid hormone, it may re-grow if thyroid hormone is stopped. Because suppressive therapy with thyroid hormone may have adverse effects on the heart and bones, many doctors are stopping thyroid hormone, assessing changes in nodule size and then deciding whether thyroid hormone should be restarted. Nodules that grow need reassessment, either a repeat biopsy or surgical excision.