Lasting disappearance of autonomously functioning thyroid nodule (AFTN) following the TSH stimulation test

Two AFTNs in one thyroid lobe were detected in a eumetabolic woman, with complete suppression of uptake in the paranodular tissue. After TSH stimulation, performed 2 months later, uptake was found in paranodular tissue only, both nodules being cold on the 131I scan. The same distribution of 131I was found on the next scan after a further 2 months without stimulation. Cystic degeneration was found by sonography and confirmed by aspiration biopsy. The destruction of one of the AFTNs was incomplete, as witnessed by a reappearance of function after 16 months. No differences in the thyroid handling of pertechnetate and iodide were detected. It is believed that the TSH stimulation might have hastened the otherwise spontaneous degenerative changes in the AFTNs.