Solitary autonomously functioning thyroid lesions. Diagnosis, clinical features and pathogenetic considerations.

One hundred sixty-four patients with autonomously functioning thyroid lesions (AFTL), 140 with nontoxic and 24 with toxic lesions, were studied over 12 years. To avoid pitfalls in diagnosis of nontoxic AFTL, a suppression procedure should precede the repeat scan after the administration of thyroid stimulating hormone. Women outnumbered men by 13 to 1 for nontoxic AFTL and 3.8 to 1 for toxic AFTL. Larger and toxic lesions were found in older patients, suggesting their derivation from smaller nontoxic lesions. Serum triiodothyronine (T3) and thyroxine concentrations exhibited parallel deviations from average normal levels for most of 29 patients with hot AFTL. T3 toxicosis was not seen. Ultrasound was more sensitive than scanning in detecting cystic degeneration. Observation was advised for patients with nontoxic AFTL unless toxicity appeared imminent. Of 51 such patients, followed from 1 to 12 years, none became hyperthyroid, but 10 AFTL increased from slightly to fourfold in size or showed evidence of degeneration. Of 24 patients with toxic AFTL, 20 were treated with radioiodine and the remaining 4 surgically; surgery is the preferred treatment for patients under 40 years of age. Three of 29 patients who were treated surgically had thyroid cancer. Since AFTL have histologic and pathophysiologic features characteristic of benign endocrine neoplasms, the association with cancer may be more than coincidental.