Thyroid dysfunction in preterm neonates exposed to iodine

Iodine Metabolism and Thyroid Function During the Perinatal Period: Maternal-Neonatal Correlation and Effects of Topical Povidone-Iodine Skin Disinfectants

An adequate maternal iodine intake during pregnancy and lactation is essential for growth and mental development in fetuses and newborns. There are limited data on perinatal iodine metabolism in mothers and infants, as well as the effect of povidone-iodine (PVP-I) antiseptics used in cesarean delivery. The urinary iodine concentration (UIC), serum iodine, thyrotropin (TSH), free thyroxine (FT4), and breast milk iodine concentration (BMIC) were measured consecutively in a total of 327 mothers and 249 term-infants in two prospective studies. The maternal median UIC was 164 μg/L in the third trimester, increased to 256 μg/L at 44 h after birth, and then decreased to 116 μg/L 1 month later. The BMIC on the 4th and 32th postpartum days was 17.6 and 13.5 μg/100 g, respectively. In neonatal infants born to the mothers unexposed to PVP-I, the median UIC was 131 μg/L in the first voiding urine and increased to 272 μg/L on day 4 and then slightly decreased to 265 μg/L on day 28 suggesting sufficient iodine reserve at birth. PVP-I antiseptics containing 1 g of iodine for skin preparation at cesarean delivery transiently increased maternal serum iodine concentration (1.9-fold), UIC (7.8-fold) at 41 h after surgery and BMIC, while it had little effect on maternal TSH, FT4, and neonatal UIC, TSH, or FT4. The iodine status of pregnant women and their infants was adequate in this population; however, the UIC in lactating mothers at one postpartum month was low enough to suggest iodine deficiency or near iodine deficiency. Further studies are necessary.

Congenital Hypothyroidism: Screening and Management

ABSTRACT

Untreated congenital hypothyroidism (CH) leads to intellectual disabilities. Prompt diagnosis by newborn screening (NBS) leading to early and adequate treatment results in grossly normal neurocognitive outcomes in adulthood. However, NBS for hypothyroidism is not yet established in all countries globally. Seventy percent of neonates worldwide do not undergo NBS.The initial treatment of CH is levothyroxine, 10 to 15 mcg/kg daily. The goals of treatment are to maintain consistent euthyroidism with normal thyroid-stimulating hormone and free thyroxine in the upper half of the age-specific reference range during the first 3 years of life. Controversy remains regarding detection of thyroid dysfunction and optimal management of special populations, including preterm or low-birth weight infants and infants with transient or mild CH, trisomy 21, or central hypothyroidism.Newborn screening alone is not sufficient to prevent adverse outcomes from CH in a pediatric population. In addition to NBS, the management of CH requires timely confirmation of the diagnosis, accurate interpretation of thyroid function testing, effective treatment, and consistent follow-up. Physicians need to consider hypothyroidism in the face of clinical symptoms, even if NBS thyroid test results are normal. When clinical symptoms and signs of hypothyroidism are present (such as large posterior fontanelle, large tongue, umbilical hernia, prolonged jaundice, constipation, lethargy, and/or hypothermia), measurement of serum thyroid-stimulating hormone and free thyroxine is indicated, regardless of NBS results.

Evidence-based review of chlorhexidine gluconate and iodine in the preoperative skin preparation of young infants

PURPOSE

The preoperative preparation of young infants' skin requires special considerations. Commonly used solutions for preparing the skin preoperatively include chlorhexidine (CHG) and iodine. The Centers for Disease Control and Prevention (CDC) has recommendations for preparing skin for surgery and other invasive procedures for adults, but they do not have recommendations for young infants' skin. The purpose of this evidence-based literature review is to synthesize the literature, compare, and inform healthcare providers about the safety and efficacy of CHG and iodine as preoperative preparation solutions for young infants' skin. For this project young infants is defined as infants less than 48 weeks' postmenstrual age and those born prematurely and less than 28 days old.

CONCLUSIONS

We analyze 19 articles that met the inclusion criteria. Three discussion themes emerge: systemic absorption, dermatologic burns, and CHG and iodine efficacy.

PRACTICE IMPLICATIONS

We need more research regarding the safety and efficacy of CHG and iodine solutions for preoperative preparation of young infants' skin. Findings suggest the cautious use of CHG and iodine solutions on patients born at or before 28 weeks' postmenstrual age, especially those less than 28 days postnatal age.

The effects of topical iodine containing antiseptics on thyroidal status and early neurodevelopment of preterm infants

OBJECTIVES

The goal of this study was to determine the quality of these disinfectants' effects on thyroid function and neurological scores in premature newborns aged 28 to 36 gestational weeks (GW).

METHODS

This cohort study was conducted from October 2020 to September 2021 among 28-36 GW preterm infants at the neonatal care unit of Jiangnan University Hospital. We divided this 12 month period into two consecutive 6 month periods. Composite iodine disinfectants and alcohol are used for skin and umbilical cord disinfection of preterm infants, respectively. Urinary iodine concentration (UIC), thyroid hormone levels, and neonatal behavioral and neurological assessment (NBNA) scores were determined in both groups.

RESULTS

A total of 126 patients were included in the study, 65 in the iodine exposed group and 61 in the alcohol group. The second UIC and the incidence of serum T4≤5 μg/dL and TSH≥10 mIU/L in the iodine exposed group were significantly higher than those in the alcohol group (p<0.05). The first NBNA score was lower in the iodine exposed group than in the alcohol group (p<0.05). However, whether it has clinical significance remains to be explored. There was a linear relationship between the two NBNA scores (iodine exposure group, R ²=0.344; alcohol group, R ²=0.227). No sepsis or other adverse outcomes occurred in the two groups of preterm infants after disinfection with different disinfectants.

CONCLUSIONS

Iodine-containing disinfectants seem to have the potential to cause an increased rate of thyroid dysfunction and a decreased neurological score and should be evaluated in further studies.

Utility of Repeat Testing for Congenital Hypothyroidism in Infants with Very Low Birth Weight

OBJECTIVE

To assess for possible missed hypothyroidism in infants of very low birth weight (VLBW) whose initial newborn screening (NBS) was within normal reference range.

STUDY DESIGN

We analyzed serum thyroid-stimulating hormone (TSH) obtained at 36 weeks of corrected gestational age or at hospital discharge if earlier (retest TSH) in infants with VLBW in the neonatal intensive care unit to determine the prevalence and factors associated with retest TSH ≥5 mU/L, a concentration requiring close follow-up for hypothyroidism. Utility of alternative cut-offs for NBS TSH also was assessed.

RESULTS

A total of 398 infants, median gestational age 29 (range 22-36) weeks, birth weight 1138 (470-1498) g, were included in this study. Retest TSH was obtained at 49.5 (12-137) days after birth. Median retest TSH was 3.1 (0.5-27.9) mU/L. Seventy-three (18.3%) of the cohort had retest TSH ≥5 mU/L. Adjusting NBS cut-off to ≥15 or ≥10 mU/L identified <50% of infants with TSH ≥5 mU/L, resulting in 6% false positives and >70% false negatives. Multiple regression modeling indicated that 35% of variance in retest TSH value was explained by NBS TSH concentration, birth weight, and gestational age, all P < .01.

CONCLUSIONS

Retesting for hypothyroidism at 36 weeks of corrected gestational age in infants with VLBL and normal NBS could identify infants who require ongoing surveillance until thyroid function has been definitively ascertained. Adjusting NBS TSH cutoffs is not a valid option for identifying potential hypothyroidism in infants with VLBW because of lack of sensitivity and unacceptable false-positive and false-negative rates.

2021 European Thyroid Association Guidelines for the Management of Iodine-Based Contrast Media-Induced Thyroid Dysfunction

Given the fact that a large number of radiological examinations using iodine-based contrast media (ICM) are performed in everyday practice, clinicians should be aware of potential ICM-induced thyroid dysfunction (TD). ICM can induce hyperthyroidism (Hyper) or hypothyroidism (Hypo) due to supraphysiological concentrations of iodine in the contrast solution. The prevalence of ICM-induced TD varies from 1 to 15%. ICM-induced Hyper is predominantly found in regions with iodine deficiency and in patients with underlying nodular goiter or latent Graves' disease. Patients at risk for ICM-induced Hypo include those with autoimmune thyroiditis, living in areas with sufficient iodine supply. Most cases of ICM-induced TD are mild and transient. In the absence of prospective clinical trials on the management of ICM-induced TD, an individualized approach to prevention and treatment, based on patient's age, clinical symptoms, pre-existing thyroid diseases, coexisting morbidities and iodine intake must be advised. Treatment of ICM-induced Hyper with antithyroid drugs (in selected cases in combination with sodium perchlorate) should be considered in patients with severe or prolonged hyperthyroid symptoms or in older patients with underlying heart disease. It is debated whether preventive therapy with methimazole and/or perchlorate prior to ICM administration is justified. In ICM-induced overt Hypo, temporary levothyroxine may be considered in younger patients with symptoms of Hypo, with an underlying autoimmune thyroiditis and in women planning pregnancy. Additional clinical trials with clinically relevant endpoints are warranted to further aid in clinical decision-making in patients with ICM-induced TD.

Reference intervals for preterm thyroid function during the fifth to seventh day of life

BACKGROUND

Due to the lack of reference intervals for serum free triiodothyronine (FT3), free thyroxine (FT4) and thyroid stimulating hormone (TSH) in preterm neonates during the 5th to 7th day of life, we performed a retrospective study using the chemiluminescence immunoassay system.

METHODS

A total of 2040 preterm neonates with a gestational age (GA) of 26-35 weeks in the neonatal intensive care unit from 2014 to 2019 were included. Their serum FT3, FT4 and TSH values were calculated and analyzed to establish reference intervals for preterm neonates stratified by GA. The comparisons of FT3, FT4 and TSH were made by sex (males and females) and gestational age (26-28 weeks; 29-32 weeks; 33-35 weeks).

RESULTS

The reference intervals for FT3, FT4 and TSH in preterm neonates with a GA of 26-35 weeks were (1.65~5.21) pmol/L, (8.64~25.41) pmol/L, and (0.406~12.468) mlU/L, respectively. There were significant differences between serum FT3 and FT4 values and GA, while TSH levels were not significantly different (P < 0.01). The serum FT3 values of males were lower than those of females, especially in the 29-32 weeks group. No significant differences in serum values between sexes were found in FT4 or TSH (P > 0.05).

CONCLUSION

Reference intervals of thyroid function tests were established to determine the early diagnostic criteria of thyroid diseases for neonates with a GA of 26-35 weeks and to avoid unnecessary retesting and interventions. The reference intervals of FT4 can be used as an indicator to regulate the doses of thyroid hormone supplement in the treatments of congenital hypothyroidism.

Severe hypothyroidism following a single topical exposure to iodine in a premature neonate

A neonate, born at 24 weeks, underwent a patent ductus arteriosus ligation, with previous normal thyroid stimulating hormone (TSH) levels, developed severe hypothyroidism from topical exposure to iodine following a single surgical procedure at 28 days of life. A low free T4 level of 0.05 ng/dL and a high TSH level of 228 mIU/L was detected with an increased urinary iodine excretion level of 178 mg/L (reference range 0.30-1.97 mg/L). The thyroid ultrasound was normal. Levothyroxine was started immediately but thyroid function did not recover fully during admission and levothyroxine was required beyond term corrected. This case highlighted how susceptible extremely preterm infants are to iodine induced hypothyroidism, even short-term topical exposure. Delayed treatment of hypothyroidism can lead to profound neurodevelopmental delay. As surgical advances allow for interventions at earlier gestations, the importance of early thyroid function testing postexposure to iodine is highlighted and ultimately topical iodine should be avoided in these susceptible infants.

Chlorhexidine Gluconate Utilization for Infection Prevention in the NICU: A Survey of Current Practice

BACKGROUND

Central-line-associated bloodstream infection (CLABSI) contributes to significant morbidity and mortality in the neonatal intensive care unit (NICU). Disinfection of skin is part of bundled cares aimed at prevention of CLABSI. While considered an essential component of insertion and maintenance bundles, the optimal solution to disinfect neonatal skin remains controversial.

PURPOSE

The purpose of this project was to survey neonatal nurse practitioners and nursing leaders across NICUs regarding the current use of chlorhexidine gluconate (CHG) in term and preterm infants.

METHODS

This descriptive study involved the collection of survey data to determine NICU practices related to the use of CHG in their infant population. The sample was composed of nursing directors of NICUs and neonatal nurse practitioners who completed an electronic survey via a provided link.

FINDINGS/RESULTS

Chlorhexidine was reported to be used in 53 (82.81%) of the NICUs and was the primary agent used to prepare the skin for central vascular catheter insertion (53.23%) followed by povidone-iodine (45.16%), and 70% isopropyl alcohol (1.61%). Gestational age or birth weight restrictions for CHG use were reported in 43 (82.69%) NICUs. Trends in the data demonstrated nursing's role in using CHG in the NICU. Adverse events reported from CHG included burns, redness, dermatitis, and other irritations. Concerns included risk of absorption, burns, skin irritation, lack of evidence, and overall safety.

IMPLICATIONS FOR PRACTICE

Systematic monitoring by nurse leaders is needed to identify evidence related to skin disinfection and CHG in neonates. Targeted education for nursing staff related to directed to developmental maturation of the skin, safe use of CHG, review of best evidence, rationale for usage of CHG, and potential iatrogenic effects is recommended.

IMPLICATIONS FOR RESEARCH

Research is needed to evaluate the impact of educational offerings and surveillance for adverse events on CLABSI rates.

How can the occurrence of delayed elevation of thyroid stimulating hormone in preterm infants born between 35 and 36 weeks gestation be predicted?

Objective

We evaluated frequency and risk factors of delayed TSH elevation (dTSH) and investigated follow-up outcomes in the dTSH group with venous TSH (v-TSH) levels of 6–20 mU/L according to whether late preterm infants born at gestational age (GA) 35–36 weeks had risk factors.

Methods

The medical records of 810 neonates (414 boys) born at Seoul National University Hospital who had a normal neonatal screening test (NST) and underwent the first repeat venous blood test at 10–21 days post birth were reviewed.

Results

Seventy-three (9.0%) neonates showed dTSH, defined as a v-TSH level ≥6.0 mU/L, 12 of whom (1.5%) were started on levothyroxine medication. A multivariate-adjusted model indicated that a low birth weight (LBW <2,000 g), a congenital anomaly, and exposure to iodine contrast media (ICM) were significant predictors for dTSH (all p < 0.05). Among these 73 dTSH infants, all 5 infants with TSH levels ≥20 mU/L began levothyroxine medication, and 6 of 16 infants with v-TSH levels of 10–20 mU/L were indicated for levothyroxine, regardless of coexisting risk factors. However, only 1 of 52 infants with v-TSH levels of 6–10 mU/L who had a congenital anomaly was indicated for levothyroxine. All healthy late preterm infants, including LBW and multiple births, with v-TSH levels of 6–10 mU/L exhibited normal thyroid function.

Conclusions

dTSH was detected in 9.0% and levothyroxine was indicated in 1.5% of infants born at GA 35–36 weeks, particularly those with a LBW, a congenital anomaly, or history of ICM exposure. Either levothyroxine or retesting is indicated for late preterm neonates with TSH levels ≥10 mU/L regardless of risk factors. If healthy preterm neonates show v-TSH levels of 6–10 mU/L, a second repeat test may not be necessary; however, further studies are required to set a threshold for retesting.

Does the use of an iodine-containing contrast agent to visualise the PICC tip in preterm babies cause hypothyroidism? A randomised controlled trial

AIM

To compare thyroid function tests in preterm neonates (<30 weeks and >48 hour old) exposed to iodine-based contrast with controls and ascertain the certainty of peripherally inserted central catheter (PICC) tip position.

METHODS

Infants requiring a PICC were randomised to receive 0.3 mL of iodine-containing contrast or normal saline. The primary outcome was the difference in thyroid-stimulating hormone (TSH) levels on day 14 post PICC insertion and on day 28 of life.

RESULTS

41 infants were randomised with no significant differences in TSH level (mIU/L) at day 14 post PICC insertion (3.1 vs 2) or on day 28 of life (2.2 vs 1.7). The PICC tip was more easily localised in the contrast group (85% vs 55%). Urinary iodine levels were significantly increased in the contrast-exposed group.

CONCLUSION

Use of contrast did not suppress subsequent thyroid function and helped visualise the PICC tip with more certainty.

CLINICAL TRIAL REGISTRATION NUMBER

ACTRN12614000560695, pre-result.

Central line-associated bloodstream infections in neonates

Newborn infants, including premature infants, are high-risk patients susceptible to various microorganisms. Catheter-related bloodstream infections are the most common type of nosocomial infections in this population. Regular education and training of medical staffs are most important as a preventive strategy for central line-associated bloodstream infections (CLABSIs). Bundle approaches and the use of checklists during the insertion and maintenance of central catheters are effective measures to reduce the incidence of CLABSIs. Chlorhexidine, commonly used as a skin disinfectant before catheter insertion and dressing replacement, is not approved for infants <2 months of age, but is usually used in many neonatal intensive care units due to the lack of alternatives. Chlorhexidine-impregnated dressing and bathing, recommended for adults, cannot be applied to newborns. Appropriate replacement intervals for dressing and administration sets are similar to those recommended for adults. Umbilical catheters should not be used longer than 5 days for the umbilical arterial catheter and 14 days for the umbilical venous catheter. It is most important to regularly educate, train and give feedback to the medical staffs about the various preventive measures required at each stage from before insertion to removal of the catheter. Continuous efforts are needed to develop effective and safe infection control strategies for neonates and young infants.

Early Identification of Primary Hypothyroidism in Neonates Exposed to Intralymphatic Iodinated Contrast: A Case Series

CONTEXT

In neonates, iatrogenic hypothyroidism can result from topical or IV iodine exposure. Data on intralymphatic iodine exposure, risk factors for disease severity, and timing of hypothyroidism are limited.

CASE DESCRIPTIONS

We report 4 cases of premature neonates with previously normal thyroid function tests (TFTs) who developed hypothyroidism after intralymphatic iodinated contrast. Patients 1 and 2, premature infants with complex medical histories, had chylous effusions and high-volume chest tube output requiring imaging with lymphangiograms on day of life (DOL) 97 and DOL 43, respectively. They developed severe, primary hypothyroidism with TSH of 335.7 mIU/mL (reference range, 1.7 to 9.1) on DOL 111 and TSH of 470.2 mIU/mL (reference range, 1.7 to 9.1) on DOL 68. Patient 3 had prenatally diagnosed fetal hydrops manifesting with chylous effusions and high-volume chest tube output. The infant underwent lymphangiography on DOL 90 and was noted to have an elevated TSH of 13.35 mIU/mL (reference range, 1.7 to 9.1) 4 days later with spot urine iodine of 1742 µg/L (normal, <200). Patient 4 had a lymphatic malformation and underwent sclerotherapy with doxycycline with intralymphatic iodine exposure on DOL 4 and was found to have a TSH of 16.7 µU/mL (reference range, 1.7 to 9.1) 3 days later with spot urine iodine of 228,712 µg/L (normal, <200). The TFT results for all patients improved after levothyroxine administration.

CONCLUSION

Intralymphatic iodine should be considered a major risk factor in the development of iatrogenic primary hypothyroidism, especially in premature neonates soon after exposure. Close monitoring of TFTs is imperative to avoid potential long-term adverse outcomes in this population.

Effect of iodinated contrast medium on thyroid function: a study in children undergoing cardiac computed tomography

BACKGROUND

Few studies, and with conflicting results, have evaluated the potential effects of iodinated contrast media on children's thyroid function.

OBJECTIVE

To investigate the effects of iodinated contrast medium on thyroid function in neonates, infants and young children with congenital heart disease undergoing cardiac computed tomography (CT).

MATERIALS AND METHODS

We retrospectively evaluated 10 neonates (group 1) and 23 infants and young children (group 2) without thyroid or renal disease for serum levels of thyroid-stimulating hormone, free triiodothyronine and free thyroxine before contrast-enhanced cardiac CT, 48 h after CT and at discharge from the hospital. Cardiac CT was performed with intravenous administration of 1.14±0.17 mL/kg of body weight of iopromide (containing 370 mg of iodine/mL).

RESULTS

Group 1 had a reduction of thyroid-stimulating hormone from baseline to 48 h post injection (P=0.002). Group 2 had a reduction of thyroid-stimulating hormone median levels from baseline to 48 h post injection and an increase from 48 h to discharge (P=0.0005 and P=0.0001, respectively).

CONCLUSION

Intravenous iodinated contrast medium in children with congenital heart disease caused transient thyroid-stimulating hormone decrease 48 h after CT, with thyroid-stimulating hormone returning to normal range at discharge.

Congenital Hypothyroidism

Congenital hypothyroidism is common and can cause severe neurodevelopmental morbidity. Prompt diagnosis and treatment are critical to optimizing long-term outcomes. Universal newborn screening is an important tool for detecting congenital hypothyroidism, but awareness of its limitations, repeated screening in high-risk infants, and a high index of clinical suspicion are needed to ensure that all affected infants are appropriately identified and treated. Careful evaluation will usually reveal the etiology of congenital hypothyroidism, which may inform treatment and prognosis. Early and adequate treatment with levothyroxine results in excellent neurodevelopmental outcomes for most patients with congenital hypothyroidism.

Pediatric Hypothyroidism: Diagnosis and Treatment

Thyroid hormone has important physiologic functions in nearly every organ system. The critical role of thyroid hormone in growth and in physical and neurologic development lends particular importance to the prompt diagnosis and appropriate treatment of hypothyroidism in infants and children. Congenital hypothyroidism is common and has potentially devastating neurologic consequences. While the approach to diagnosis and treatment of severe congenital hypothyroidism is well established, data continue to emerge about the genetic causes, clinical significance, and prognosis of the milder forms of congenital hypothyroidism that are increasingly being diagnosed by newborn screening. Similarly, the diagnosis and treatment of severe acquired hypothyroidism is straightforward and clearly of clinical benefit, but uncertainty remains about the optimal management of mild subclinical hypothyroidism. This review summarizes current knowledge of the causes, clinical manifestations, diagnosis, treatment, and prognosis of hypothyroidism in infants and children, with a focus on recent developments and areas of uncertainty in this field.