Iodine nutrition and thyroid diseases in Chengdu, China: an epidemiological study

OBJECTIVE: To assess the iodine nutritional status and investigate the prevalence of thyroid diseases in a community population in Chengdu, China. METHODS: Eighty school-age children were randomly selected for measurements of urinary iodine concentration. A total of 1500 residents over the age of 18 who had lived in Chengdu for more than 5 years were selected by stratified cluster sampling. Serum thyroid hormone concentrations and thyroid autoantibodies were measured, and thyroid ultrasonography was performed. RESULTS: The median urine iodine concentration was 184 µg/l in school-age children. The prevalence of clinical hyperthyroidism, subclinical hyperthyroidism, clinical hypothyroidism and subclinical hypothyroidism was 0.97%, 1.95%, 0.90% and 5.55%, respectively. The prevalence of thyroid autoantibodies and thyroid nodules was 15.82% and 16.87%, respectively. The prevalence of clinical hyper- and hypothyroidism was greater in females than in males (P < 0.05). The prevalence of subclinical hyper- and hypothyroidism, thyroid nodules and thyroid autoantibodies increased significantly with age (P < 0.05). The rate of new abnormal TSH was 9.37%, and the average serum Thyroid Stimulating Hormone (TSH) concentrations increased with age. When TSH >0.71 mU/l, the prevalence of positive TPOAb and/or TgAb increased significantly with rising concentrations of TSH (P < 0.05); however, the prevalence of thyroid nodules did not increase with escalating concentrations of TSH (P = 0.09). CONCLUSION: Subclinical thyroid diseases, especially subclinical hypothyroidism and thyroid nodules, are common in an iodine sufficient area. Females and the elderly might benefit from routine screening for thyroid diseases, followed by appropriate detection and treatment.