Serum TSH,FT 3,and FT 4 Levels in Inhabitants of an Endemic Goiter Area in China Supplied Iodized Salt for Twenty-five Years

The thyroid function and TSH concentration of villagers in an endemic goiter area in China where iodized salt had been supplied for twenty-five years were surveyed. We found that the serum FT₃ and TSH (IRMA) levels of villagers were higher and the FT₄ level was lower than those of the controls, which suggested that the inhabitants of the endemic goiter area had subclinical hypothyroidism based on the ultrasensitive method for TSH assay. Therefore, we suggest that the best biochemical techniques for monitoring the iodized salt prophylaxis program and the physiological response of villagers to iodine are measurements of serum TSH level and FT₄ level periodically.