The importance of iodine nutrition during pregnancy - clinical aspect.

Iodine is an essential constituent of thyroid hormones. Thyroid hormones regulate brain development, growth and metabolism of the human body. Inadequately low iodine intake and decreased thyroid hormone synthesis can lead to iodine deficiency disorders. The severity of disorders depends not only on the degree of iodine deficiency, but also on the stage of the human development. Many areas of the world, including the Czech Republic, have been affected by natural iodine deficiency and the incidence of iodine deficiency disorders has been historically high. Fortification of food-grade salt was an effective step towards reduction of iodine deficiency impact. Although the Czech Republic has been considered to be an iodine sufficient area since 2004, iodine deficiency is still a threat to subgroups of population with an increased demand for iodine, such as pregnant women and newborns. Moreover, these groups are particularly sensitive to even mild iodine deficiency, because it could permanently affect the cognitive development of the fetus and have a negative effect on the course of pregnancy. Conversely, in other groups of the population steps taken to prevent iodine deficiency diseases may lead to excessive iodine intake with potential risks. It is necessary to control the iodine fortification and regularly monitor the iodine status of the population considering the individual risk groups.

Iodine supply and thyroid function in women with gestational diabetes mellitus: a cohort study.

Introduction: Maternal urinary iodine concentration and blood neonatal thyroid-stimulating hormone (TSH) concentration reflect iodine status in pregnancy and serve as markers of iodine deficiency. As dietary measures in gestational diabetes mellitus (GDM) could affect iodine intake, our study aimed to investigate iodine supply in women with GDM compared to healthy pregnant women and to evaluate its relationship to maternal and neonatal thyroid function. Methods: Urinary iodine concentration (UIC) and serum TSH, free thyroxine (FT4), and autoantibodies against thyroid peroxidase (TPOAb) were analyzed in 195 women with GDM and 88 healthy pregnant women in the second trimester. Subsequently, neonatal TSH concentrations measured 72 h after delivery in a subgroup of 154 newborns (115 of mothers with GDM and 39 controls) from the national register were analyzed. Results: Median UIC was significantly lower in women with GDM compared to controls (89.50 µg/L vs. 150.05 µg/L; P < 0.001). Optimal iodine intake was found only in nine women with GDM (4.6%) and 33 healthy pregnant women (37.5%) (P < 0.001). Most pregnant women with GDM (88.7%) compared to one half of controls (50%) had iodine deficiency (P < 0.001). Although serum TSH and the prevalence of hypothyroidism (TSH > 4.0 mIU/L) were not different in both groups, hypothyroxinaemia was more prevalent in GDM compared to controls (12.3% vs 3.4%, P = 0.032). Consistently, neonatal TSH > 5.0 mIU/L indicating iodine deficiency, was found in 6 (5.2%) newborns of women with GDM as compared to none in controls. In women with GDM, the prevalence of perinatal complications was significantly lower in those who were taking dietary iodine supplements compared to those who were not (3/39 (7.69%) vs 46/156 (28.85%), P <0.001). In the multiple logistic and linear regression models in women with GDM, hypothyroxinaemia was associated with preterm births, and a negative association of serum FT4 and HbA1c was found. Conclusion: Iodine deficiency in pregnancy was more prevalent among women with GDM compared to healthy pregnant controls. Serum FT4 negatively correlated with HbA1c, and hypothyroxinaemia was associated with preterm births in women with GDM. Conversely, women with GDM who used dietary iodine supplements had a lower risk of perinatal complications.

Thyroid nodules and thyroid cancer in women with positive thyroid screening in pregnancy: a double-centric, retrospective, cohort study.

OBJECTIVE: Thyroid nodules are a common finding in the general population. The primary aim of the study was to determine the prevalence of thyroid nodules and cancer found by ultrasound (US) in women who underwent screening for thyroid dysfunction during pregnancy. DESIGN: A double-centric, retrospective, cohort study. PATIENTS AND METHODS: We searched through medical records, including thyroid ultrasonography, of pregnant women who were positively screened for thyroid disorders (using thyroid-stimulating hormone and thyroid antibodies) from an unselected population ('universal screening group', n = 690) and of women who underwent the testing based on the presence of clinical risk factors defined by American Thyroid Association ('case-finding group', n = 249). RESULTS: Prevalence of benign and malignant thyroid nodules was lower in the 'universal screening group' than in the 'case-finding group' (9.9% vs 17.7%, P= 0.002, and 0.9% vs 7.2%, P< 0.001, respectively). Consistently, the thyroid cancer rate was lower among the nodules in the 'universal screening group' than in the 'case-finding group' (8.1% vs 29.0%, P= 0.003). Ultrasound EU-TIRADS (European Thyroid Imaging and Reporting Data System) category ≥4 had a 95.8% sensitivity for thyroid cancer. In palpable nodules, the prevalence of cancer was significantly higher than in the non-palpable ones (44.0% vs 2.2%, P < 0.001). In a multivariate regression analysis, thyroid nodules were associated with a history of infertility and parity. CONCLUSIONS: Compared to the data from cancer registries, universal screening allowed detecting thyroid cancer in pregnancy three to five times more frequently, but the cancer rate among nodules (8.1%) did not differ from the common population. US had very good sensitivity for thyroid cancer in pregnancy.