Potential Preventive Effect of Selenium on Iodine-induced Thyroid Autoimmunity During Pregnancy
Potential Preventive Effect of Selenium on Iodine-induced Thyroid Autoimmunity During Pregnancy
In 1994, the WHO and UNICEF Joint Committee on Health Policy recommended Universal Salt
 Iodization as a safe, cost-effective and sustainable strategy to ensure sufficient intake of
 iodine by all individuals. However, it is still absent in Latvia.

 A recent countrywide study in 2013 shows iodine deficiency among pregnant women in Latvia: 81
 % of pregnant women had UIC levels below the WHO recommended range of 150-250 mcg/g Cr.

 Because mild to moderate iodine deficiency during pregnancy can adversely affect fetal brain
 development, WHO-UNICEF and ICCIDD advise an increase in the recommended daily dosage of
 iodine to 250 mcg/day for pregnant women and breastfeeding women and 150 mcg/day for women in
 the preconception period.

 Data from a survey of the Latvian population indicate that approximately 100 mcg of iodine
 per day is consumed through foods and iodized salt. To meet the increased iodine requirement
 in pregnancy, pregnant women should take a supplement containing 150 mcg of iodine daily from
 the earliest time possible.

 A sudden increase in iodine intake in an iodine-deficient population may increase thyroid
 autoimmunity. It is evident that thyroid disease has multiple adverse effects during
 pregnancy and in the developing fetus especially in women with elevated serum anti-thyroid
 antibody titers.

 Studies have considered supplementing with selenium to reduce the risk of auto-immune
 thyroiditis/post-partum autoimmune thyroid disease. Of the 11 trials of selenium
 supplementation in patients with autoimmune thyroiditis, 7 have shown benefit with treatment
 for 6 months or longer.

 Aim of study is to approve that 150 mcg of iodine daily improves iodine status in pregnant
 women and iodine 150 mcg in combination with selenium 100 mcg daily reduce risk of thyroid
 autoimmunity.

 Hypothesis of study is that 150 mcg iodine daily during pregnancy improves iodine status.
 Iodine in combination with selenium is less associated with thyroid autoimmunity.

 Study design: Pregnant women are randomized for either 150 mcg iodine intake daily or 150 mcg
 iodine combined with 100 mcg selenium daily. Interventional group is compared with controls
 without particular iodine supplementation.

 Participants are asked to complete a questionnaire on dietary habits concerning iodine.
 Thyroid function (thyroid-stimulating hormone, free thyroxine) and thyroperoxidase antibodies
 (TPO-Ab) and urinary iodine are measured during first, second and third trimester of
 pregnancy and week 8 after delivery in both, intervention and control group.
In 1994, the WHO and UNICEF Joint Committee on Health Policy recommended Universal Salt
 Iodization as a safe, cost-effective and sustainable strategy to ensure sufficient intake of
 iodine by all individuals. However, universal salt iodization is still absent in Latvia.

 A recent countrywide study in 2013 shows iodine deficiency among pregnant women in Latvia.
 The median Cr-standardized UIC was 80.8 (interquartile range (IQR) 46.1-130.6) mcg/g Cr or
 69.4 (IQR 53.9-92.6) mcg/L during pregnancy, and 81 % of pregnant women had UIC levels below
 the WHO recommended range of 150-250 mcg/g Cr.

 Because mild to moderate iodine deficiency during pregnancy can adversely affect fetal brain
 development, WHO-UNICEF and ICCIDD advise an increase in the recommended daily dosage of
 iodine to 250 mcg/day for pregnant women and breastfeeding women and 150 mcg/day for women in
 the preconception period.

 Data from a survey of the Latvian population indicate that approximately 100 mcg of iodine
 per day is consumed through foods and iodized salt. To meet the increased iodine requirement
 in pregnancy, pregnant women should take a supplement containing 150 mcg of iodine daily from
 the earliest time possible.

 A sudden increase in iodine intake in an iodine-deficient population may increase thyroid
 autoimmunity. Studies have connected induction of disease processes with thyroglobulin (Tg)
 iodination, because hypo-iodinated Tg did not activate T cells; however, increasing the Tg
 iodine content to even normal levels in vitro led to antigenicity of the molecule. It is
 evident that thyroid disease has multiple adverse effects during pregnancy and the postpartum
 period, and in the developing fetus especially in women with elevated serum anti-thyroid
 antibody titers.

 Previous studies have considered supplementing with selenium to reduce the risk of
 auto-immune thyroiditis/post-partum autoimmune thyroid disease. Potential mechanisms may be
 related to the selenoenzyme, GPx3, removing excess H2O2 produced in the thyrocyte for the
 iodination of tyrosine to give thyroid hormones, thereby preventing thyrocyte damage.
 Additionally, selenoprotein S (SEPS1) is involved in the control of the inflammatory response
 in the endoplasmic reticulum. Of the 11 trials of selenium supplementation in patients with
 autoimmune thyroiditis, 7 have shown benefit with treatment for 6 months or longer.

 Aim of study is to approve that 150 mcg of iodine daily improves iodine status in pregnant
 women and iodine 150 mcg in combination with selenium 100 mcg daily reduce risk of thyroid
 autoimmunity.

 Hypothesis of study is that 150 mcg iodine daily during pregnancy improves iodine status.
 Iodine in combination with selenium is less associated with thyroid autoimmunity.

 Study design: Pregnant women are randomized for either 150 mcg iodine intake daily or 150 mcg
 iodine combined with 100 mcg selenium daily. Interventional group is compared with controls
 without particular iodine supplementation.

 Participants are asked to complete a questionnaire on dietary habits concerning iodine intake
 at the moment they are recruited for study, at third trimester of pregnancy and week 8 after
 delivery.

 Thyroid function (thyroid-stimulating hormone (TSH), free thyroxine (fT4) and thyroperoxidase
 antibodies (TPO-Ab) measures are assessed during first, second and third trimester of
 pregnancy and week 8 after delivery in both, intervention and control group. Blood samples
 are sent to the E. Gulbis Laboratory (Riga, Latvia), which operates according to EN ISO
 15189:2008 standard. TSH, fT4 and TPO-Ab are measured by chemiluminescence immunoassay
 (Siemens, Malvern, PA, USA).

 Urinary iodine, using the ammonium persulfate method, is also measured in first, second,
 third trimester of pregnancy and postpartum week 8 in intervention and control groups.

 The urinary creatinine concentration is measured using the Jaffe method with the intention
 that iodine concentration adjusted for creatinine concentration (iodine/Cr) could be
 calculated. Creatinine standardized UIC is a more reliable method of iodine excretion than
 random spot UIC measurement since there is a great day-to-day variability in water intake.

 Statistical analysis includes pairwise comparison of 1) median (interquartile range) urinary
 iodine concentration, median (IQR) or mean (SD) TSH, and median (IQR) or mean (SD) fT4; 2)
 proportion (95%CI) of women with UIC below 150 mcg, TSH above trimester-specific norm, and
 positive TPO antibodies among all three study groups at specific follow-up intervals.
 Mann-Whitney U test or two-sided t-test is used for comparing continuous variables, whereas
 chi2 test (or Fisher exact test) is used to compare proportions. If significant differences
 observed at baseline, the change in those parameters from visit to visit is calculated and
 compared. Logistic regression analysis is used to compare intervention groups with control
 group in order to adjust for differences in baseline characteristics.
Inclusion Criteria:

 -  healthy women before 10 weeks of gestation

 -  signed informed consent form

 Exclusion Criteria:

 -  pre-existing thyroid disease

 -  pregnancy after assisted reproductive technologies

 -  known hypersensitivity reaction to iodine or selenium, or other components of dietary
 supplement used in the study