[Urinary iodide excretion in Japanese people and thyroid dysfunction].

In order to assess the Japanese dietary iodine intake, we examined the urinary iodine excretion of those on an ordinary Japanese diet chosen at random and observed whether the thyroid function might affect the amounts of urinary iodine excretion. The subjects consisted of cases of untreated hypothyroidism and chronic thyroiditis (CT) and euthyroid controls who were healthy people or had non-thyroidal disorders such as diabetes mellitus or hypertension. Eight cases of hypothyroidism were composed of 3 cases of secondary hypothyroidism with empty sella syndrome and 5 cases of primary hypothyroidism and 32 patients with CT have been maintained in euthyroid states with T4 medication. We selected 32 cases of sex and age-matched healthy people as controls. The mean levels of excreted urinary iodine were 465.6 micrograms/day in the healthy controls and 471.8 micrograms/day in patients with CT, respectively. Urinary iodine excretion was significantly correlated to serum inorganic iodide in both controls and CT patients, of which correlation coefficients were +0.35 and +0.5, respectively. Urinary iodine and serum inorganic iodide ratios (U/S) in hypothyroidism were significantly (p less than 0.05) depressed compared with those in CT. The present study indicated that recent Japanese dietary iodine intake was estimated to be approximately 470 micrograms/day and that the urinary iodine excretion would be influenced not only by iodine intake but also by thyroid function.