Background: Knowledge about the population's iodine status is important, because it allows adjustment of iodine supply and prevention of iodine deficiency. The validity and comparability of iodine-related population studies can be improved by standardization, which was one of the goals of the EUthyroid project. The aim of this study was to establish the first standardized map of iodine status in Europe by using standardized urinary iodine concentration (UIC) data. Materials and Methods: We established a gold-standard laboratory in Helsinki measuring UIC by inductively coupled plasma mass spectrometry. A total of 40 studies from 23 European countries provided 75 urine samples covering the whole range of concentrations. Conversion formulas for UIC derived from the gold-standard values were established by linear regression models and were used to postharmonize the studies by standardizing the UIC data of the individual studies. Results: In comparison with the EUthyroid gold-standard, mean UIC measurements were higher in 11 laboratories and lower in 10 laboratories. The mean differences ranged from −36.6% to 49.5%. Of the 40 postharmonized studies providing data for the standardization, 16 were conducted in schoolchildren, 13 in adults, and 11 in pregnant women. Median standardized UIC was <100 μg/L in 1 out of 16 (6.3%) studies in schoolchildren, while in adults 7 out of 13 (53.8%) studies had a median standardized UIC <100 μg/L. Seven out of 11 (63.6%) studies in pregnant women revealed a median UIC <150 μg/L. Conclusions: We demonstrate that iodine deficiency is still present in Europe, using standardized data from a large number of studies. Adults and pregnant women, particularly, are at risk for iodine deficiency, which calls for action. For instance, a more uniform European legislation on iodine fortification is warranted to ensure that noniodized salt is replaced by iodized salt more often. In addition, further efforts should be put on harmonizing iodine-related studies and iodine measurements to improve the validity and comparability of results.

Article: Effect of excess iodine intake on thyroid on human health - Minerva Medica 2017 April;108(2):136-46 - Minerva Medica - Journals

Background: The absorption of levothyroxine (LT4) is affected by many factors. Bariatric surgery is recommended in severely obese patients. The aim of this study was to determine the consequences of bariatric surgery on LT4 pharmacokinetic parameters, and to identify the regions of the gastrointestinal tract where LT4 is absorbed in patients with severe obesity before and after surgery. Methods: We studied 32 severely obese nonhypothyroid patients who underwent sleeve gastrectomy (SG; n=10), Roux-en-Y gastric bypass (RYGBP; n=7), or biliopancreatic diversion with long limbs (BPD-LL; n=15). Before surgery, from 8:00 a.m., blood samples were collected before and every 30 minutes after the oral administration of a solution of 600 μg of LT4. The same procedure was repeated 35 days after surgery. We estimated the pharmacokinetic parameters of LT4 before and after surgery, including the area under the curve (AUC), the peak thyroxine concentration (C_max), and the time to peak thyroxine concentration (T_max). Results: Following surgery, in the SG group, the mean AUC was higher than it was before surgery (18.97±6.01 vs. 25.048±6.47 [μg/dL]·h; p<0.01), whereas the values of C_max and T_max were similar to those before surgery. In the RYGBP group, mean AUC, C_max, and T_max were similar before and after surgery. In the BPD-LL group, mean AUC and C_max were higher after surgery than before (14.18±5.64 vs. 25.51±9.1 [μg/dL]·h, p<0.001; 5.62±1.34 vs. 8.16±2.57 μg/dL, p<0.001, respectively), whereas T_max was similar. Conclusions: The pharmacokinetic parameters of LT4 absorption are improved following SG and BPD-LL types of bariatric procedures. We conclude that the stomach, the duodenum, and the upper part of the jejunum are not sites for LT4 absorption, because in the above-mentioned bariatric procedures these are bypassed or removed.

Background: Adequate dietary iodine consumption, predicted via the urinary iodine concentration (UIC), is necessary for normal thyroid function and for the neurodevelopment of fetuses and neonates. The general population of Greece is considered to be iodine sufficient, but our preliminary findings suggest that Greek pregnant women are at risk of iodine deficiency. Objective: Our aim was to estimate the thyroid function and UIC in a representative population of pregnant Greek women. Methods: UIC and thyroid function were assessed in 1,118 women from 19 representative areas of the country. Results: The median UIC was found to be 127.1 µg/l (range 7.8-2,296), which is indicative of insufficient iodine intake according to the standard of the World Health Organization (WHO) for pregnant women. The median UIC was below the minimal recommended value of 150 µg/l in 61% of the women, and below 100 or 50 µg/l in 32 and 7%, respectively. An optimal iodine intake (150-250 µg/l) was observed in 26%, and was over the cut-off of 500 µg/l in 2% of the subjects. Serum thyrotropin significantly increased between trimesters, from 1.57 ± 1.2, to 1.68 ± 1.0 and to 2.02 ± 1.2 mU/l (p < 0.001). Serum-free thyroxine decreased significantly between trimesters, from 1.22 ± 0.34, to 1.01 ± 0.21 and 0.96 ± 0.2 ng/ml (p < 0.05). Serum thyroglobulin levels remained unchanged over the trimesters and were not correlated with UIC. Conclusions: While the general population of Greece is iodine sufficient, these findings suggest that, according to the WHO, the majority of pregnant Greek women are iodine deficient. These data strongly suggest that a proactive policy should be developed to lower iodine deficiency risk in this population of women.

Objective: To assess the reliability of thyroglobulin (Tg) as a marker of iodine status during pregnancy. Design: 299 women aged 30.5 ± 4.8 years (mean ± SD) were studied. Methods: In every subject, we measured urinary iodine concentration (UIC), serum thyrotropin (TSH), Tg, free thyroxine (fT₄), Tg autoantibodies (TgAbs) and human chorionic gonadotropin (hCG) levels. We excluded samples with increased TgAbs from the analysis. Results: According to WHO criteria, the study population was iodine deficient in every trimester. Serum Tg levels did not differ during the three trimesters of pregnancy. Serum hCG levels fell significantly as pregnancies advanced. A weak, significantly negative correlation (limited to the 3rd trimester) was found between Tg and UIC (ρ = -0.187, p = 0.039). Serum fT₄ decreased as pregnancies advanced and TSH increased. Serum fT₄ was negatively correlated with TSH (ρ = -0.161, p = 0.006) and positively with hCG (ρ = +0.165, p = 0.005). The multiple regression equation of Tg based on hCG, TSH, UIC and trimester of pregnancy was significant but weak (F = 4.057, p = 0.003; R² = 0.055), with hCG as a significant predictor Tg (p for log hCG = 0.041). Conclusions: Tg cannot be considered as a valid marker of iodine deficiency in pregnancy, at least in a mildly iodine-deficient environment. Further studies in a larger patient cohort with differences in iodine status, as well as studies on Tg changes after improving iodine status in pregnant women, are needed in order to corroborate these results.