Urinary Iodine Excretion is Low and Serum Thyroglobulin High in Pregnant Women in Parts of Denmark

Abstract

In the Randers area of Denmark urinary iodine excretion (which reflects iodine intake) was found to be much lower than recommended intake levels, both in women in late pregnancy [52(23-118) micrograms iodine/g creatinine, median, range, n = 20] and in non-pregnant controls [42(23-71), n = 20]. Serum thyroglobulin which is high in iodine deficiency was 32.5 micrograms/l (median) (range 10.5-78.0) in the control women and considerably higher in the pregnant women [67.0 micrograms/l (9.0-385)]. This increase was probably due to the extra iodine requirement of pregnancy which was not satisfied with an adequate increase in iodine intake. The results may suggest that pregnant women in this area should receive iodine supplementation and that a general program of iodine supplementation should be considered.

Thyroglobulin as a Biomarker of Iodine Deficiency: A Review

“…Seven studies (21,25,30,38,43,45,46) showed that iodine deficient adults had a median Tg ‡13 lg/L (range 16-69 lg/L), while only one study (45) reported that iodine-sufficient adults had a median Tg ‡ 13 lg/L. However, 8 of 12 studies (21,25,(42)(43)(44)72,90,91) reported that adults who were categorized as iodine deficient had a median Tg <13 lg/L.…”

“…Two of the eight studies (78,79) assessed Tg concentration in iodine-deficient women throughout their pregnancy (i.e., in each trimester); in one study (79), a median Tg <13 lg/L was observed in all three trimesters, and in one study (78), a Tg ‡13 lg/L was reported in the first and third trimesters, but it was <13 lg/L in the second trimester. Although six of eight studies (37,38,74,75,77,79) collected information on the use of iodine supplements in pregnancy, of these, only one study (37) reported that the Tg concentration of women taking iodine supplements was significantly lower compared with women who did not take supplements (i.e., difference of *15 lg/L). We are unaware of any published studies of pregnant women with adequate iodine status that include measures of both UIC and Tg.…”

“…Six of eight studies (37,38,(74)(75)(76)(77) reported that iodine-deficient pregnant women (either first, second, or third trimester, or at delivery) had a median Tg ‡13 lg/L (range 16-67 lg/L). Two of the eight studies (78,79) assessed Tg concentration in iodine-deficient women throughout their pregnancy (i.e., in each trimester); in one study (79), a median Tg <13 lg/L was observed in all three trimesters, and in one study (78), a Tg ‡13 lg/L was reported in the first and third trimesters, but it was <13 lg/L in the second trimester.…”

“…Of these, nine were randomized controlled trials, two were nonrandomized controlled trials, three were cohort observational studies, 23 were cross-sectional studies (10 multicenter), and one was a monitoring report of iodization programs that included a measurement before the introduction of iodized salt to a measurement after the introduction of iodized salt. In order to investigate the consistency of the relationship between iodine status as determined by UIC and Tg more clearly, for those studies that reported this information for more than one group, we considered each of these groups separately (i.e., one study of pregnant women and their newborns (37); one study of pregnant women and adults (38); one study of children and adults (30); three studies of children living in different regions (39) or countries (40,41); and seven studies of adults living in different regions (21,25,(42)(43)(44) or countries (45,46)). …”

Serum thyroglobulin before and after iodization of salt: an 11-year DanThyr follow-up study

“…Since then RIAs and screening for Tg autoantibodies (Tg-Ab) were improved (12) and several studies found an inverse association between iodine intake and serum Tg (13,14,15,16,17). Therefore, it has been suggested that serum Tg values in a population is a sensitive marker of iodine intake, and that serum Tg can be used to monitor the iodine status of a population.…”