The Effects of Iodine Supplementation in Pregnancy on Iodine Status, Thyroglobulin Levels and Thyroid Function Parameters: Results from a Randomized Controlled Clinical Trial in a Mild-to-Moderate Iodine Deficiency Area

Background: Iodine supplementation during pregnancy in areas with mild-to-moderate iodine deficiency is still debated. Methods: A single-center, randomized, single-blind and placebo-controlled (3:2) trial was conducted. We enrolled 90 women before 12 weeks of gestation. From enrollment up until 8 weeks after delivery, 52 women were given an iodine supplement (225 ug/day, potassium iodide tablets) and 38 were given placebo. At recruitment (T0), in the second (T1) and third trimesters (T2), and 8 weeks after delivery (T3), we measured participants’ urinary iodine-to-creatinine ratio (UI/Creat), thyroid function parameters (thyroglobulin (Tg), TSH, FT3, and FT4), and thyroid volume (TV). The newborns’ urinary iodine concentrations were evaluated in 16 cases. Results: Median UI/Creat at recruitment was 53.3 ug/g. UI/Creat was significantly higher in supplemented women at T1 and T2. Tg levels were lower at T1 and T2 in women with UI/Creat ≥ 150 ug/g, and in the Iodine group at T2 (p = 0.02). There was a negative correlation between Tg and UI/Creat throughout the study (p = 0.03, r = −0.1268). A lower TSH level was found in the Iodine group at T3 (p = 0.001). TV increased by +Δ7.43% in the Iodine group, and by +Δ11.17% in the Placebo group. No differences were found between the newborns’ TSH levels on screening the two groups. Conclusion: Tg proved a good parameter for measuring iodine intake in our placebo-controlled series. Iodine supplementation did not prove harmful to pregnancy in areas of mild-to-moderate iodine deficiency, with no appreciable harmful effect on thyroid function.

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Earliest prevention of endemic goiter by iodine supplementation during pregnancy

Acta Endocrinologica ◽

10.1530/eje.0.1340443 ◽

1996 ◽

Vol 134 (4) ◽

pp. 443-448 ◽

Cited By ~ 90

Author(s):

Klaus Peter Liesenkötter ◽

Wolfgang Göpel ◽

Ulrich Bogner ◽

Barbara Stach ◽

Annette Grüters

Keyword(s):

Thyroid Function ◽

Iodine Deficiency ◽

Endemic Goiter ◽

Urinary Iodine ◽

Thyroid Volume ◽

Urinary Iodine Excretion ◽

Thyroid Peroxidase ◽

Iodine Supplementation ◽

Iodine Excretion ◽

Maternal Thyroid

Liesenkötter KP, Göpel W, Bogner U, Stach B, Grüters A. Earliest prevention of endemic goiter by iodine supplementation during pregnancy. Eur J Endocrinol 1996;134:443–8. ISSN 0804–4643 During pregnancy complex changes of maternal thyroid function occur and they are influenced by the maternal iodine supply. It has been demonstrated that with decreasing iodine supply maternal goiter and hypothyroxinemia as well as fetal and neonatal hypothyroidism become more prevalent. Therefore iodine supplementation during pregnancy is now strongly recommended also in areas of moderate iodine deficiency. To monitor the success of iodine supplementation and its theoretical risk of increasing the frequency of thyroid autoantibodies, we have investigated the thyroid volume, thyroid function, urinary iodine excretion and antibodies to thyroid peroxidase at 10–12 weeks of gestation and postpartum in 38 mothers receiving 300 μg potassium iodide/day and in 70 mothers without iodine supplementation. In all of their newborns thyroid volume was determined by ultrasound. The thyrotropin (TSH) levels and antibodies to thyroid peroxidase (TPO-ab) in the neonates were measured in dried blood spots on filter paper from their newborn screening. Urinary iodine excretion was increased significantly after iodine supplementation in mothers (p < 0.001) and their newborns (<0.05). No hypo- or hyperthyroidism was observed in the mothers or newborns. Interestingly, no difference of maternal thyroid volumes was observed between the two groups after pregnancy, but the volumes of the thyroid glands in newborns of mothers who received iodine were significantly (p < 0.004) lower (0.7 ± 0.4 ml) than in the control group (1.5 ± 1.1 ml). There was no change in the frequency of TPO-ab in either group after pregnancy. In four mothers transplacental passage of these antibodies was documented by positive measurement in the blood sample of the newborn. This study documents that iodine supplementation during pregnancy in an area of moderate iodine deficiency results in a lower size of neonatal thyroid volume and that this supplementation was not accompanied by an increase in the frequency of TPO-ab. Klaus Peter Liesenkötter, Kinderklinik Kaiserin Auguste Victoria Haus (KAVH), Virchow-Klinikum der Medizinische Fakultät der Humboldt-Universität zu Berlin, Heubnerweg 6, 14059 Berlin, Germany

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Study of Urinary Iodine Level Assessment and its Relation to Thyroid Function during Pregnancy

QJM ◽

10.1093/qjmed/hcab100.103 ◽

2021 ◽

Vol 114 (Supplement_1) ◽

Author(s):

Magda Shoukry Mohamed ◽

Merhan Samy Nasr ◽

Salah Hussien El-Halawany ◽

Ahmed Mohamed Abbas ◽

Salma Said Hassan Tayeh

Keyword(s):

Iodine Deficiency ◽

Urinary Iodine ◽

Thyroid Volume ◽

Significant Negative Correlation ◽

Iodine Deficiency Disorders ◽

Iodine Excess ◽

Salt Iodization ◽

Excess Iodine ◽

Iodine Supplementation ◽

Iodine Level

Abstract Background The global effort to prevent iodine deficiency disorders through iodine supplementation, such as universal salt iodization, has achieved impressive progress during the last few decades. However, iodine excess, due to extensive environmental iodine exposure in addition to poor monitoring, is currently a more frequent occurrence than iodine deficiency. Iodine excess is a precipitating environmental factor in the development of autoimmune thyroid disease. Aim of the study to evaluate the urinary iodine level as a marker of iodine status in pregnant women in 3rd trimester and assess its relation to thyroid functions. Patients and Methods This Cross Sectional Study was conducted on 100 subjects with their ages ranging from 18-35 years old, pregnant females, at the third trimester, selected from Obstetric Out- patient Clinic of Ain shams University Hospitals. Samples were collected from participants in cairo, during the Spring and Summer from March to August. Results in our study, there was a significant negative correlation between Urinary Iodine level and TSH as Iodine difficient group has the Highest TSH, and the Highest Thyroid Volume, as there was a significant negative correlation between Urinary Iodine level and Thyroid Volume. Conclusion TSH level and Thyroid Volume were global effort to prevent iodine deficiency disorders through iodine supplementation, such as universal salt iodization, has achieved impressive progress during the last few decades. However, iodine excess, due to extensive environmental iodine exposure in addition to significantly higher in Iodine difficient group than Excess iodine group, And FT4 level was lower in Iodine difficient group than excess iodine group.

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Iodine Intake and Thyroid Function in Pregnant Women in a Private Clinical Practice in Northwestern Sydney before Mandatory Fortification of Bread with Iodised Salt

Journal of Thyroid Research ◽

10.1155/2012/798963 ◽

2012 ◽

Vol 2012 ◽

pp. 1-6 ◽

Cited By ~ 10

Author(s):

Norman Blumenthal ◽

Karen Byth ◽

Creswell J. Eastman

Keyword(s):

Pregnant Women ◽

Thyroid Function ◽

Iodine Deficiency ◽

Urinary Iodine ◽

Iodine Intake ◽

Urinary Iodine Excretion ◽

Blood Collection ◽

Antenatal Visit ◽

Urinary Iodine Concentration ◽

Cross Sectional

Aim. The primary objective of the study was to assess the iodine nutritional status, and its effect on thyroid function, of pregnant women in a private obstetrical practice in Sydney.Methods. It was a cross-sectional study undertaken between November 2007 and March 2009. Blood samples were taken from 367 women at their first antenatal visit between 7 and 11 weeks gestation for measurement of thyroid stimulating hormone (TSH) and free thyroxine (FT4) levels and spot urine samples for urinary iodine excretion were taken at the same time as blood collection.Results. The median urinary iodine concentration (UIC) for all women was 81 μg/l (interquartile range 41–169 μg/l). 71.9% of the women exhibited a UIC of <150 μg/l. 26% of the women had a UIC <50 μg/l, and 12% had a UIC <20 μg/l. The only detectable influences on UIC were daily milk intake and pregnancy supplements. There was no statistically significant association between UIC and thyroid function and no evidence for an effect of iodine intake on thyroid function.Conclusions. There is a high prevalence of mild to moderate iodine deficiency in women in Western Sydney but no evidence for a significant adverse effect on thyroid function. The 6.5% prevalence of subclinical hypothyroidism is unlikely to be due to iodine deficiency.

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HYPOTHYROIDISM AND GOITER IN A YOUNG MALE WITH SUSPECTED DIETARY IODINE DEFICIENCY FOLLOWED BY THYROTOXICOSIS AFTER IODINE SUPPLEMENTATION

AACE Clinical Case Reports ◽

10.4158/accr-2019-0180 ◽

2020 ◽

Vol 6 (1) ◽

pp. e19-e22

Author(s):

Itivrita Goyal ◽

Manu Raj Pandey ◽

Rajeev Sharma

Keyword(s):

Thyroid Gland ◽

Thyroid Function ◽

Iodine Deficiency ◽

Urinary Iodine ◽

Young Male ◽

Free Thyroxine ◽

Thyroid Function Tests ◽

Normal Range ◽

Iodine Supplementation ◽

Function Tests

Objective: Iodine deficiency disorders (IDDs) remain a major public health concern in most parts of the world but are extremely rare in North America. We describe a case of goiter in a young male with dietary history and findings suggestive of IDD. Methods: Laboratory and imaging procedures including thyroid function tests, autoantibodies, urine iodine, thyroid ultrasound, and radioactive iodine (RAI) uptake scan were performed. Results: On initial presentation, thyroid-stimulating hormone (TSH) was 24.4 mIU/L (normal range is 0.4 to 5.0 mIU/L), free thyroxine was <0.4 ng/dL (normal range is 0.8 to 1.8 ng/dL), and thyroid peroxidase antibody was positive at 43 IU/mL (normal range is <35 IU/mL). He reported consuming strawberries and peanut butter sandwiches with no intake of dairy or seafood due to gastrointestinal issues (abdominal pain, bloating, and nausea). Physical exam revealed a diffusely enlarged, palpable thyroid gland (grade II goiter). Ultrasound of the neck showed an enlarged thyroid gland with no nodules. RAI uptake scan showed diffuse increased uptake (91%). Given his poor diet, a 24-hour urinary iodine excretion test was ordered which was suggestive of very low iodine intake. He was started on multivitamins with 150 μg of iodine daily. On follow up, clinical exam showed grade I goiter and TSH had normalized to 0.7 mIU/L and free thyroxine was 1.2 ng/dL. He continued on iodine supplementation and tolerated iodine-rich foods. Six months later, thyroid function tests showed hyperthyroidism with TSH of <0.002 ng/dL and free thyroxine was elevated to 2.8 ng/dL. Iodine supplements were stopped. Conclusion: Hypothyroidism and goiter due to IDD should be suspected in the setting of poor dietary intake. IDDs can be rapidly diagnosed in a patient on a restricted diet with multiple urinary iodine determinations and RAI study. Regular thyroid labs should be done to monitor for hyperthyroidism that can develop after iodine supplementation.

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High prevalence of iodine deficiency in pregnant women living in adequate iodine area

Endocrine Connections ◽

10.1530/ec-18-0131 ◽

2018 ◽

Vol 7 (5) ◽

pp. 762-767 ◽

Cited By ~ 9

Author(s):

Verônica Carneiro Borges Mioto ◽

Ana Carolina de Castro Nassif Gomes Monteiro ◽

Rosalinda Yossie Asato de Camargo ◽

Andréia Rodrigues Borel ◽

Regina Maria Catarino ◽

...

Keyword(s):

Pregnant Women ◽

Thyroid Function ◽

Iodine Deficiency ◽

Urinary Iodine ◽

Thyroid Volume ◽

Adverse Outcomes ◽

Urinary Iodine Concentration ◽

Serum Thyroglobulin ◽

Cross Sectional ◽

Iodine Status

Objectives Iodine deficiency during pregnancy is associated with obstetric and neonatal adverse outcomes. Serum thyroglobulin (sTg) and thyroid volume (TV) are optional tools to urinary iodine concentration (UIC) for defining iodine status. This cross-sectional study aims to evaluate the iodine status of pregnant women living in iodine-adequate area by spot UIC and correlation with sTg, TV and thyroid function. Methods Two hundred and seventy-three pregnant women were evaluated at three trimesters. All had no previous thyroid disease, no iodine supplementation and negative thyroperoxidase and thyroglobulin antibodies. Thyroid function and sTg were measured using electrochemiluminescence immunoassays. TV was determined by ultrasonography; UIC was determined using a modified Sandell–Kolthoff method. Results Median UIC was 146 µg/L, being 52% iodine deficient and only 4% excessive. TSH values were 1.50 ± 0.92, 1.50 ± 0.92 and 1.91 ± 0.96 mIU/L, respectively, in each trimester (P = 0.001). sTg did not change significantly during trimesters with median 11.2 ng/mL and only 3.3% had above 40 ng/mL. Mean TV was 9.3 ± 3.4 mL, which positively correlated with body mass index, but not with sTg. Only 4.5% presented with goitre. When pregnant women were categorized as iodine deficient (UIC < 150 µg/L), adequate (≥150 and <250 µg/L) and excessive (≥250 µg/L), sTg, thyroid hormones and TV at each trimester showed no statistical differences. Conclusions Iodine deficiency was detected frequently in pregnant women living in iodine-adequate area. sTg concentration and TV did not correlate to UIC. Our observation also demonstrated that the Brazilian salt-iodization programme prevents deficiency, but does not maintain iodine status within adequate and recommended ranges for pregnant women.

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Maternal Iodine Status and Thyroid Function during Pregnancy

Journal of Medicine ◽

10.3329/jom.v10i2.2815 ◽

1970 ◽

Vol 10 (2) ◽

pp. 56-59 ◽

Cited By ~ 1

Author(s):

Tahrim Mehdi ◽

Md Mozammel Hoque ◽

Zinnat Ara Nasreen ◽

Farzana Shirin ◽

Md Maqsudul Hakim Khan

Keyword(s):

Thyroid Function ◽

Iodine Deficiency ◽

Urinary Iodine ◽

Thyroid Status ◽

Iodine Nutrition ◽

Iodine Status ◽

Iodine Supplementation ◽

Iodine Level ◽

Thyroid Hormone Concentration ◽

Serum Tsh

Background: Pregnant ladies are most likely to develop relative iodine deficiency during pregnancy to affect thyroid function in our population unless specific dietary care or therapeutic iodine supplementation is taken into account which is yet to be materialized. Methods: In this cohort study sixty uncomplicated normal pregnant women were enrolled in 1st trimester and followed up till delivery. In every trimester maternal iodine status & thyroid status were determined by urinary iodine & serum thyroid hormone concentration respectively. Results: Women progressively become more iodine deficient & tends to be hypothyroid as pregnancy advances. At 3rd trimester of pregnancy maternal Urinary Iodine found to be negatively correlated with their serum TSH. Conclusion: During pregnancy women develop iodine deficiency which adversely affects the thyroid function. So adequate iodine monitoring and iodine nutrition during pregnancy is necessary. Keywords: Urinary iodine level, TSH, FT3, FT4. doi: 10.3329/jom.v10i2.2815 J MEDICINE 2009; 10 : 56-59

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Longitudinal trends in thyroid function in relation to iodine intake: ongoing changes of thyroid function despite adequate current iodine status

Acta Endocrinologica ◽

10.1530/eje-13-0589 ◽

2014 ◽

Vol 170 (1) ◽

pp. 49-54 ◽

Cited By ~ 15

Author(s):

Annenienke C van de Ven ◽

Romana T Netea-Maier ◽

H Alec Ross ◽

Teun A E van Herwaarden ◽

Suzanne Holewijn ◽

...

Keyword(s):

Thyroid Function ◽

Iodine Deficiency ◽

Urinary Iodine ◽

Iodine Intake ◽

Thyroid Peroxidase ◽

Urinary Iodine Concentration ◽

Creatinine Concentration ◽

Iodine Status ◽

The Past ◽

Urine Iodine

ObjectiveSeveral cross-sectional studies on populations with iodine deficiency showed that TSH-levels are negatively associated with age, while in populations with high iodine intake TSH is positively associated with age. The question is whether such an age-thyroid function relation is an ongoing process apparent also in longitudinal studies and whether it reflects an actual iodine deficiency or an iodine insufficiency in the past.MethodsIn an area with a borderline iodine status in the past, we studied 980 participants of the Nijmegen Biomedical Study. We measured serum TSH, free thyroxine (FT4), total triiodothyronine (T3), peroxidase antibodies, and the urine iodine and creatinine concentration 4 years after our initial survey of thyroid function, in which we reported a negative association between TSH and age.ResultsWithin 4 years, TSH decreased by 5.4% (95% CI 2.5–8.3%) and FT4increased by 3.7% (95% CI 2.9–4.6%). Median urinary iodine concentration was 130 μg/l. Estimated 24-h iodine excretion was not associated with TSH, T3, change of TSH, or FT4over time or with the presence of antibodies against thyroid peroxidase. Only FT4appeared to be somewhat higher at lower urine iodine levels: a 1.01% (95% CI 0.17–1.84%) higher FT4for each lower iodine quintile.ConclusionsIn this longitudinal study, we found an ongoing decrease in TSH and increase in FT4in a previously iodine insufficient population, despite the adequate iodine status at present. This suggests that low iodine intake at young age leads to thyroid autonomy (and a tendency to hyperthyroidism) that persists despite normal iodine intake later in life.

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Oral iodine supplementation in very low birth weight infants. Thyroid function and Neurodevelopmental follow up at 24 months. A Randomized Clinical Trial

10.21203/rs.3.rs-316884/v1 ◽

2021 ◽

Author(s):

Susana Ares ◽

BELEN SAENZ-RICO ◽

JUAN ARNAEZ ◽

Jesus Diez-Sebastian ◽

Felix Omeñaca ◽

...

Keyword(s):

Breast Milk ◽

Thyroid Hormones ◽

Preterm Infants ◽

Thyroid Function ◽

Iodine Deficiency ◽

Iodine Content ◽

Iodine Intake ◽

Control Group ◽

Premature Babies ◽

Iodine Supplementation

Abstract The trace element iodine (I) is essential for the synthesis of thyroid hormones. Premature babies need >30 µg I / kg /day (ICCIDD recommendations). Neonates and especially preterm infants are a population at risk of suffering the consequences of iodine deficiency, because of the impact of neonatal hypothyroxinemia on brain development. The main aim of this project is to prevent the mental retardation and increased risk of cerebral palsy of premature infants, which is partially caused by neonatal hypothyroxinemia. We gave Oral iodine supplementation in very premature babies during the neonatal period. Population: we included 94 infants born <1500g. Intervention group: we administered 30 µg I / kg /day of iodine in oral drops to 47 infants from first day of life until hospital discharge. Control group: 47 infants without supplements. The study was approved by the Ethics Committee. Samples of different formulas, maternal milk was kept for the determination of the iodine content. Interventions: Blood, food and urine samples (collected at 1, 7, 15, 21, 30 days after birth and at discharge). Measurements: milk and urine for iodine determination (Benotti method). Blood samples: for thyroid hormones (T4, free T4, T3 and TSH) and tyroglobulin. Their neurological development was assessed at 2 years of age (Bayley Test).Iodine content of mothers´ breast milk: 15 (5.0) µg I /dL (range 1-60); Infants in the supplemented group reached the recommendations from the first days of life. Infants in the control group did not reach the recommended intake of iodine to 60 days of life. We found a positive relation between iodine intake and the concentrations of thyroid hormones until 60 days of life. Conclusions: Thyroid function is related to iodine intake in preterm infants. Breast milk appears to be the best source of iodine for the premature infant. Preterm babies on formula preparations and with exclusive parenteral nutrition are at high risk of iodine deficiency. Therefore, supplements should be added if iodine intake is found to be inadequate.

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A survey of iodine intake and thyroid volume in Dutch schoolchildren: reference values in an iodine-sufficient area and the effect of puberty

Acta Endocrinologica ◽

10.1530/eje.0.1440595 ◽

2001 ◽

pp. 595-603 ◽

Cited By ~ 60

Author(s):

WM Wiersinga ◽

J Podoba ◽

M Srbecky ◽

M van Vessem ◽

HC van Beeren ◽

...

Keyword(s):

The Netherlands ◽

Iodine Deficiency ◽

Reference Values ◽

Dietary Habits ◽

Urinary Iodine ◽

Thyroid Volume ◽

Iodine Concentration ◽

Iodine Intake ◽

Height Velocity ◽

Urinary Iodine Concentration

BACKGROUND: Iodine deficiency and endemic goiter have been reported in the past in The Netherlands, especially in the southeast. OBJECTIVE: To evaluate iodine intake and thyroid size in Dutch schoolchildren, contrasting those living in a formerly iodine-deficient region in the east (Doetinchem) with those living in an iodine-sufficient region in the west (Amsterdam area). DESIGN: Cross-sectional survey of 937 Dutch schoolchildren aged 6--18 years, of whom 390 lived in the eastern and 547 in the western part of the country. METHODS: Thyroid size was assessed by inspection and palpation as well as by ultrasound. Iodine intake was evaluated by questionnaires on dietary habits and by measurement of urinary iodine concentration. RESULTS: Eastern and western regions were similar with respect to median urinary iodine concentration (15.7 and 15.3 microg/dl, NS, Mann-Whitney U test), goiter prevalence by inspection and palpation (0.8 and 2.6%, P=0.08, chi-squared test), and thyroid volumes. The P97.5 values of thyroid volumes per age and body surface area group were all lower than the corresponding sex-specific normative WHO reference values. Iodized salt was not used by 45.7% of households. Daily bread consumption was five slices by boys and four slices by girls. Weekly milk consumption was 3 liters by boys and 2 liters by girls. Seafish was consumed once monthly. From these figures we calculated a mean daily iodine intake of 171 microg in boys and 143 microg in girls, in good agreement with the measured median urinary concentration of 16.7 microg/dl in boys and 14.5 microg/dl in girls. The sex difference in iodine excretion is fully accounted for by an extra daily consumption of one slice of bread (20 microg I) and one-seventh of a liter of milk (8.3 microg I) by boys. Thyroid volume increases with age, but a steep increase by 41% was observed in girls between 11 and 12 years, and by 55% in boys between 13 and 14 years, coinciding with peak height velocity. Girls have a larger thyroid volume at the ages of 12 and 13 years, but thyroid volume is larger in boys as of the age of 14 years. CONCLUSIONS: (1) Iodine deficiency disorders no longer exist in The Netherlands. (2) Bread consumption remains the main source of dietary iodine in The Netherlands; the contribution of iodized table salt and seafish is limited. (3) The earlier onset of puberty in girls renders their thyroid volume larger than in boys at the age of 12--13 years, but boys have a larger thyroid volume as of the age of 14 years.

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Oral Iodine Supplementation in Very Low Birth Weigh Infants. Thyroid Function and Neurodevelopmental Follow Up at 24 Months. A Randomized Clinical Trial

Annals of Thyroid Research ◽

10.26420/annalsthyroidres.2021.1075 ◽

2021 ◽

Vol 7 (1) ◽

Author(s):

Ares S ◽

◽

Arnaez J ◽

Saenz Rico B ◽

Diez J ◽

...

Keyword(s):

Breast Milk ◽

Thyroid Hormones ◽

Preterm Infants ◽

Thyroid Function ◽

Iodine Deficiency ◽

Iodine Content ◽

Iodine Intake ◽

Control Group ◽

Premature Babies ◽

Iodine Supplementation

Background: The trace element Iodine (I) is essential for the synthesis of thyroid hormones. Premature babies need >30μg I/kg/day (ICCIDD recommendations). Neonates and especially preterm infants are a population at risk of suffering the consequences of iodine deficiency, because of the impact of neonatal hypothyroxinemia on brain development. Aims: The main aim of this project is to prevent the mental retardation and increased risk of cerebral palsy of premature infants, which is partially caused by neonatal hypothyroxinemia. We gave Oral iodine supplementation in very premature babies during the neonatal period. Methods: Population: we included 94 infants born <1500g. Intervention group: we administered 30μg I/kg /day of iodine in oral drops to 47 infants from first day of life until hospital discharge. Control group: 47 infants without supplements. The study was approved by the Ethics Committee. Samples of different formulas, maternal milk was kept for the determination of the iodine content. Interventions: Blood, food and urine samples (collected at 1, 7, 15, 21, 30 days after birth and at discharge). Measurements: milk and urine for iodine determination (Benotti method). Blood samples: for thyroid hormones (T4, free T4, T3 and TSH) and tyroglobulin. Their neurological development was assessed at 2 years of age (Bayley Test). Results: Iodine content of mothers´ breast milk: 15 (5.0) μg I/dL (range 1-60); Infants in the supplemented group reached the recommendations from the first days of life. Infants in the control group did not reach the recommended intake of iodine to 60 days of life. We found a positive relation between iodine intake and the concentrations of thyroid hormones until 60 days of life. Conclusion: Thyroid function is related to iodine intake in preterm infants. Breast milk appears to be the best source of iodine for the premature infant. Preterm babies on formula preparations and with exclusive parenteral nutrition are at high risk of iodine deficiency. Therefore, supplements should be added if iodine intake is found to be inadequate. Acknowledgments. We are grateful to the Fondo de Investigaciones Sanitarias (National Grant 06/1310 for financial support).

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