The relationship between iodine intake and serum thyroglobulin in the general population.

The relationship is shown between a concentration of urinary iodine and serum thyroglobulin in population studies carried out on a general population that was randomly selected from the registry of the General Health Insurance Company (individuals aged 6-98 years, 1751 males, 2420 females). The individuals were divided into subgroups with a urinary iodine concentration of /=300 microg/l. The mean and median of thyroglobulin were calculated in these subgroups. Tg concentrations were dependent on gender (malesthyroglobulin increased with age) and statistically significant negative relationship was observed between thyroglobulin and urinary iodine in individuals with urinary iodine <300 microg/l and the age under 65 years. Upper nonparametric tolerance limits of thyroglobulin in relation to iodine intake were calculated in subgroup of normal individuals (n=1858, thyroglobulin, urinary iodine, thyrotropin and free thyroxine were within the normal reference range). Upper limits were dependent on gender and age. The total value of upper limits is 44 microg/l; for individuals aged 6-17 years it is 39.1 microg/l; 18-65 years = 51.4 microg/l and 66-98 years = 60.6 microg/l. In general, thyroglobulin serum concentrations higher than 40 microg/l should be an indicator for determining urinary iodine.