The changing incidence of thyroid carcinoma in Shenyang, China before and after universal salt iodization

An increase in the prevalence of thyroid disease has been found with increasing iodine intake, since universal salt iodization (USI) was instituted throughout China in 1996. The aim of this study was to analyze the incidence of thyroid carcinoma (TC) before and after USI in Shenyang, a city of northeastern China.

The pathology reports were collected from patients with thyroid diseases who underwent surgery in the First Hospital of China Medical University from January 1, 1992 to December 31, 2009. The detection rate, the constituent ratio, the changes of sex, age, and concomitant thyroid diseases of each histological type of TC were analyzed.

The detection rate of TC, papillary thyroid carcinoma (PTC), and medullary thyroid carcinoma (MTC) increased; that of follicular thyroid carcinoma (FTC) decreased; and that of undifferentiated thyroid carcinoma (UTC) showed no change after USI. The constituent ratio of PTC increased, that of FTC and UTC decreased, and that of MTC showed no change after USI. The mean age of female patients with TC decreased after USI. The incidences of PTC complicated with either nodular goiter or chronic lymphocytic thyroiditis increased after USI.

The detection rate of TC increased significantly, PTC predominated in the histological types of TC, and the mean age of female patients with TC decreased after USI. The patients with either nodular goiter or chronic lymphocytic thyroiditis under high iodine intake should be followed up.