Thyroglobulin in serum as an indicator of iodine status during pregnancy

Serum thyroglobulin and thyrotropin as well as urinary iodine concentration s were measured in healthy, pregnant Swedish (n=27) and Sudanese (n=21) wom en and the results compared with those of healthy Swedish (n=14) and Sudane se (n=20) non-pregnant controls. The median thyroglobulin concentrations la nd interquartile range) in the Swedish pregnant women for the three trimest ers were 15.5 (8 - 24), 10.5 (7 - 19) and 18.0 (13 - 25) mu g/L, respective ly. The median third trimester concentration was higher than both the first and second trimester concentrations, respectively (p<0.0001, p<0.0001). Co mpared to the control group, the Swedish pregnant women had a significantly higher median thyroglobulin concentration in the third trimester (p < 0.05 ). Among the Sudanese pregnant women, the median serum thyroglobulin concen trations land interquartile range) were 27.5 (12-40), 25.0 (15 - 43) and 30 .0 (15 - 67) mu g/L during the first, second and third trimesters, respecti vely. There were no significant differences between these concentrations. C ompared to the control group, the Sudanese pregnant women had a significant ly higher median thyroglobulin in the third trimester (p<0.01). The Sudanes e pregnant women also showed significantly higher median thyroglobulin conc entrations than the Swedish pregnant women in all the three trimesters of p regnancy (p<0.05, p<0.001 and p < 0.01, respectively). However, there were no significant differences between the two non-pregnant controls. Among the Swedish pregnant women, 40%, 23% and 30% of the subjects showed serum thyr oglobulin concentrations above 20 mu g/L during the first, second and third trimesters of pregnancy, respectively. Corresponding figures for the Sudan ese pregnant women were 55%, 61% and 64%, respectively. A significantly neg ative correlation was shown between serum thyroglobulin and urinary iodine concentrations during the second and third trimesters in the Swedish women (r=-0.8, p=0.01 and r=-0.5, p=0.03, respectively), and in the third trimest er in the Sudanese women (r=-0.6, p=0.03). No such correlation was observed between thyrotropin and urinary iodine concentration in either the Swedish or the Sudanese pregnant women. It is concluded that serum thyroglobulin i s a more sensitive indicator of iodine deficiency than serum thyrotropin du ring pregnancy.