Evolution of toxicity in solitary nontoxic autonomously functioning thyroid nodules.

Between 1961 and 1979, 349 patients with autonomously functioning thyroid nodules (AFTN) were seen. There were 287 nontoxic and 62 toxic lesions. Toxic lesions were seen in 56.5% of AFTN patients over 60 yr of age but in only 12.5% of the younger patients. The female to male ratio was 14.9:1 for nontoxic AFTN patients but only 5.9:1 for toxic AFTN patients. The proportion of toxic AFTN in patients less than 20 yr old (13.8%) was not significantly different from that in patients 20--60 yr old (12.7%). T3 toxicosis was observed in 46% of those patients with hyperthyroidism. All but 4 of the toxic AFTN measured 3 cm in diameter or larger. AFTN 3 cm or larger were more than twice as common in patients 40 yr or older than in younger patients. Of 159 untreated nontoxic AFTN patients, 14 became toxic within 1--6 yr. One patient in 5 with a nontoxic AFTN 3 cm or larger developed toxicity.