[Risk factors and prevention of thyroid carcinoma]

Thyroid carcinoma represents the most frequent endocrine tumor. Recent reports have documented an increase in the incidence of thyroid cancer. Its incidence varies geographically around the world from 0.9/ 100,000 men and 2.4/100,000 women in Great Britain to 8.8/100,000 men and 18.2/ 100,000 women in Hawaii. Radiation exposure has been strongly implicated as an aetiological factor. The greatest risk occurs with acute exposure to X and/or gamma rays, with a linear dose response curve, while the risk is inversely related to age at exposure with a latent period of 5-20 years. Together with irradiation, other factors (iodine, alcohol and calcium diet intake, hyperthyroidism, Hashi-moto's thyroiditis, Gardner syndrome, Cowden syndrome, pharmaceutical agents, hormonal factors, occupational exposure, activation of cellular oncogenes) have been associated with the risk of thyroid cancer. In prevention a policy should include regulations and methods for avoiding radiation exposure of the thyroid and for preventing nutritional deficiency and excess of iodine. Besides, early and continuous suppressive therapy of all patients affected by non-toxic goiter or treated previously with thyroidectomy, and a screening of medullary thyroid carcinoma (MTC) using pentagastrin stimulation test and restriction fragment length polymorphism analysis, in subjects with a familial history of MTC, are of paramount importance to prevent thyroid cancer.