Effects of salted food consumption on urinary iodine and thyroid function tests in two provinces in the Islamic Republic of Iran.

We evaluated sources of difference in urinary iodine between two neighbouring Iranian provinces, Gilan and Mazandaran. In the cities of Rasht (Gilan) and Sari (Mazandaran), 340 and 343 participants respectively were selected by cluster sampling. Urinary iodine in Rasht was significantly higher than in Sari (31 microg/dL versus 21 microg/dL). Sodium and potassium urine levels in Rasht were also higher than Sari. Mean daily intake of iodized salt and thyroid function tests were not significantly different. Average annual consumption of some salted foods was significantly higher in Rasht than Sari. We conclude that higher consumption of salted foods in Rasht is responsible for an increase in urinary iodine.