Part 1：A cross-sectional survey of thyroid diseases in adults in different iodine nutrition background areas.~Investigators will separately include adults ( middle-aged people and old people) in iodine-deficient, iodine-appropriate, and iodine-excessive areas. Venous blood will be collected to measure thyroid function and serum iodine. Thyroid volume and nodular disease were determined by B-ultrasonography. Drinking water, saliva and 24-h and spot urinary samples will be collected to precisely evaluate the daily iodine intake. Multiple indicators were used to accurately evaluate the iodine intake level of the subjects, and understand the differences in the prevalence of thyroid diseases in the elderly under different iodine nutrition backgrounds. Besides, the differences in thyroid disease and iodine nutritional status between young and middle-aged people and old people will be compared.~Part 2：A survey on the iodine nutrition status in the elderly with/without thyroid disease in iodine-appropriate areas.~Investigators will collect basic information (height, weight, age, other medical histories, etc.) and thyroid disease history information. Thyroid B-ultrasound and thyroid function tests were used to understand the current thyroid status of the elderly. The iodine dietary frequency questionnaire was used to assess the long-term iodine intake level of the survey subjects, and spot urinary iodine, 24-h urinary iodine and salivary iodine were used to assess the short-term iodine intake level of the survey subjects.
The aging trend of China's population is intensifying. More than 50% of the elderly in China suffer from thyroid disease. Thyroid dysfunction in the elderly increases the risk of cardiovascular and metabolic diseases. Even if thyroid-stimulating hormone (TSH) is within the normal range, brain atrophy and infarction-like vascular damage in elderly males will be aggravated with the increased TSH level. Iodine is an essential component of thyroid hormones. Iodine deficiency or excess may lead to a series of thyroid diseases. The risk threshold of iodine intake in the elderly is unknown. The goal of this observational study is to clarify the relationship between thyroid diseases and iodine intake in the elderly. The aims are:~to clarify the differences in the prevalence of thyroid diseases in the elderly with different iodine nutrition backgrounds.~to analyze the effects of mild iodine deficiency and iodine excess on the thyroid health of the elderly.~to explore the hazard threshold of iodine intake for old people.~to compare the differences in thyroid disease and iodine nutritional status between young and middle-aged people and old people.