Clinical practice: experience with newborn screening for congenital hypothyroidism in the Republic of Macedonia - a multiethnic country

Congenital Hypothyroidism in Preterm Newborns - The Challenges of Diagnostics and Treatment: A Review

Preterm newborns are forced to adapt to harsh extrauterine conditions and endure numerous adversities despite their incomplete growth and maturity. The inadequate thyroid hormones secretion as well as the impaired regulation of hypothalamus-pituitary-thyroid axis may lead to hypothyroxinemia. Two first weeks after birth are pivotal for brain neurons development, synaptogenesis and gliogenesis. The decreased level of thyroxine regardless of cause may lead to delayed mental development. Congenital hypothyroidism (CH) is a disorder highly prevalent in premature neonates and it originates from maternal factors, perinatal and labor complications, genetic abnormalities, thyroid malformations as well as side effects of medications and therapeutic actions. Because of that, the prevention is not fully attainable. CH manifests clinically in a few distinctive forms: primary, permanent or transient, and secondary. Their etiologies and implications bear little resemblance. Therefore, the exact diagnosis and differentiation between the subtypes of CH are crucial in order to plan an effective treatment. Hypothyroxinemia of prematurity indicates dynamic changes in thyroid hormone levels dependent on neonatal postmenstrual age, which directly affects patient's maintenance and wellbeing. The basis of a successful treatment relies on an early and accurate diagnosis. Neonatal screening is a recommended method of detecting CH in preterm newborns. The preferred approach involves testing serum TSH and fT4 concentrations and assessing their levels according to the cut-off values. The possible benefits also include the evaluation of CH subtype. Nevertheless, the reference range of thyroid hormones varies all around the world and impedes the introduction of universal testing recommendations. Unification of the methodology in neonatal screening would be advantageous for prevention and management of CH. Current guidelines recommend levothyroxine treatment of CH in preterm infants only when the diagnose is confirmed. Moreover, they underline the importance of the re-evaluation among preterm born infants due to the frequency of transient forms of hypothyroidism. However, results from multiple clinical trials are mixed and depend on the newborn's gestational age at birth. Some benefits of treatment are seen especially in the preterm infants born <29 weeks' gestation. The discrepancies among trials and guidelines create an urgent need to conduct more large sample size studies that could provide further analyses and consensus. This review summarizes the current state of knowledge on congenital hypothyroidism in preterm infants. We discuss screening and treatment options and demonstrate present challenges and controversies.

Risk factors for transient and permanent congenital hypothyroidism: a population-based case-control study

Background

Congenital hypothyroidism (CH) is the most important cause of mental and physical retardation in newborns. The prevalence of CH has been reported high in East Azerbaijan province of Iran. However, the risk factors for CH are poorly understood. This study aimed to determine and compare risk factors for permanent and transient CH in East Azerbaijan, Iran.

Methods

A case-control study was conducted in the Iranian national screening program for CH. This study included 680 neonates: 340 neonates with confirmed CH and 340 matched healthy controls born at the same period and from the same residential area as the cases. Multiple logistic regression analyses were used to estimate the crude and adjusted odds ratios and 95% confidence intervals for the association between different risk factors and transient and permanent CH.

Results

Out of the 680 participants, 364 (53.53%) were male. Family history of CH (OR = 5.09, 95% CI: 1.66–15.63), neonatal jaundice (OR = 3.89, 95% CI: 2.36–6.43) and parental consanguineous relation (OR = 2.19, 95% CI: 1.51–3.17) were associated with an increased risk of permanent CH. Likewise, the use of Betadine in pregnancy (OR = 4.87, 95% CI: 1.45–16.28), family history of CH (OR = 5.98, 95% CI: 2.04–17.48), neonatal jaundice (OR = 2.81, 95% CI: 1.75–4.52), parental consanguineous relation (OR = 3.86, 95% CI: 1.92–5.74), and gestational age at birth (OR = 3.2, 95% CI: 1.90–5.41) were identified as risk factors for transient CH.

Conclusion

Family history, neonatal jaundice, gestational age at birth, and Betadine usage in pregnancy are associated with CH.

Genetics of Gland-in-situ or Hypoplastic Congenital Hypothyroidism in Macedonia

Neonatal screening in Macedonia detects congenital hypothyroidism (CH) with an incidence of 1 in 1,585, and more than 50% of cases exhibit a normally located gland-in-situ (GIS). Monogenic mutations causing dyshormonogenesis may underlie GIS CH; additionally, a small proportion of thyroid hypoplasia has a monogenic cause, such as TSHR and PAX8 defects. The genetic architecture of Macedonian CH cases has not previously been studied. We recruited screening-detected, non-syndromic GIS CH or thyroid hypoplasia cases (n = 40) exhibiting a spectrum of biochemical thyroid dysfunction ranging from severe permanent to mild transient CH and including 11 familial cases. Cases were born at term, with birth weight >3,000 g, and thyroid morphologies included goiter (n = 11), thyroid hypoplasia (n = 6), and apparently normal-sized thyroid. A comprehensive, phenotype-driven, Sanger sequencing approach was used to identify genetic mutations underlying CH, by sequentially screening known dyshormonogenesis-associated genes and TSHR in GIS cases and TSHR and PAX8 in cases with thyroid hypoplasia. Potentially pathogenic variants were identified in 14 cases, of which four were definitively causative; we also detected digenic variants in three cases. Seventeen variants (nine novel) were identified in TPO (n = 4), TG (n = 3), TSHR (n = 4), DUOX2 (n = 4), and PAX8 (n = 2). No mutations were detected in DUOXA2, NIS, IYD, and SLC26A7. The relatively low mutation frequency suggests that factors other than recognized monogenic causes (oligogenic variants, environmental factors, or novel genes) may contribute to GIS CH in this region. Future non-hypothesis-driven, next-generation sequencing studies are required to confirm these findings.

Diagnostic re-evaluation of congenital hypothyroidism in Macedonia: predictors for transient or permanent hypothyroidism

BACKGROUND

Diagnostic re-evaluation is important for all patients with congenital hypothyroidism (CH) for determining the etiology and identifying transient CH cases. Our study is a first thyroxine therapy withdrawal study conducted in Macedonian CH patients for a diagnostic re-evaluation. We aimed to evaluate the etiology of CH, the prevalence of transient CH and identify predictive factors for distinguishing between permanent (PCH) and transient CH (TCH).

MATERIALS AND METHODS

Patients with CH aged >3 years underwent a trial of treatment withdrawal for 4 weeks period. Thyroid function testing (TFT), ultrasound and Technetium-99m pertechnetate thyroid scan were performed thereafter. TCH was defined when TFT remained within normal limits for at least 6-month follow-up. PCH was diagnosed when TFT was abnormal and classified according the imaging findings.

RESULTS

42 (55%) patients had PCH and 34 (45.0%) patients had TCH. Thyroid agenesia was the most prevalent form in the PCH group. Patients with TCH had lower initial thyroid-stimulating hormone (TSH) values (P < 0.0001); higher serum thyroxine levels (P = 0.0023) and lower mean doses of levothyroxine during treatment period (P < 0.0001) than patients with PCH. Initial TSH level <30.5 IU/mL and levothyroxine dose at 3 years of age <2.6 mg/kg/day were a significant predictive factors for TCH; sensitivity 92% and 100%, specificity 75.6% and 76%, respectively.

CONCLUSION

TCH presents a significant portion of patients with CH. Initial TSH value and levothyroxine dose during treatment period has a predictive role in differentiating TCH from PCH. Earlier re-evaluation, between 2 and 3 years age might be considered in some patients requiring low doses of levothyroxine.

The incidence of congenital hypothyroidism (CH) in Guangxi, China and the predictors of permanent and transient CH

BACKGROUND

The incidence of congenital hypothyroidism (CH) differs significantly among different ethnicities and regions, and early differentiation of transient CH is important to avoid unnecessary prolonged treatment with L-T4.

OBJECTIVE

To investigate the incidence of CH based on the newborn screening program in Guangxi Zhuang Autonomous Region, China, and to analyze the predictors that might allow for an early differentiation between permanent (P) and transient (T) CH.

DESIGN AND METHODS

Data from newborn screening program over a seven-year period (January 2009 to January 2016) at Guangxi Maternal and Child Health Hospital are analyzed. Blood samples were collected on filter paper between 3 and 7 days after birth, and TSH level was measured by time-resolved fluorescence assay. Individuals with increased TSH (TSH ≥ 8 IU/L) levels detected by newborn screening were recalled for further evaluation. Serum TSH, FT3 and FT4 were determined by electrochemiluminescence assay using venous blood samples. Diagnosis of CH is based on elevated TSH levels (>10 IU/L) and decreased FT4 levels (<12 pmol/L). Patients with elevated TSH levels and normal FT4 levels were diagnosed as hyperthyrotropinemia. Permanent or transient CH was determined by using the results of thyroid function tests after temporary withdrawal of L-T4 therapy at approximately 2-3 years of age.

RESULTS

Among 1,238,340 infants in the newborn screening program, 14,443 individuals were recalled for reevaluation (re-call rate 1.18%), 911 and 731 individuals were subsequently determined to have hyperthyrotropinemia and CH respectively; thus, a prevalence of 1:1359 and 1:1694 for hyperthyrotropinemia and CH. Of the 731 patients with CH, 161 patients were diagnosed with permanent CH (PCH), and 159 patients were diagnosed with transient CH (TCH), the other 411 patients are too young to determine their subtypes. Patients with PCH required an increasing dose of L-T4 during the first few years, whereas patients with TCH required a decreased dose of L-T4. The TSH levels at diagnosis and the dose of L-T4 used were significantly higher in PCH cases than in transient cases. The FT4 levels at diagnosis were significantly lower in PCH cases than in TCH cases. The TSH levels at diagnosis, FT4 levels at diagnosis and L-T4 doses at 90 days were evaluated as predictors for differentiating PCH and TCH, and their accuracy at their respective optimal cutoffs were determined to be 60.6%, 66.7% and 93.9%, respectively.

CONCLUSIONS

The CH incidence in Guangxi Zhuang Autonomous Region is slightly higher (1:1694) compared to the worldwide levels (1/2000-1/4000). The PCH and TCH ratio is close to 1; thus, the estimated PCH incidence is 1/3388, which is similar to reported worldwide average incidence (1/3000). The L-T4 dose required at 90 days (>30 μg/day) has the highest predictive value for PCH. Earlier differentiation of PCH and TCH helps to determine appropriate treatment course.

Regional Variation in the Incidence of Congenital Hypothyroidism in Macedonia

The incidence of congenital hypothyroidism (CH) is increasing in different areas around the world. Potential causes include changes in population ethnic composition, environmental factors, changing screening program methodology and lowering of TSH cutoff levels. The incidence of CH in different regions of Macedonia has not been evaluated before. A total of 251,008 newborns from all eight regions in the country have been screened between 2002 and 2015, by measurement of the thyroid-stimulating hormone (TSH) from blood spots, sampled 48-72 h after birth, using the DELFIA assay. Overall CH incidence confirmed at birth was 1/1976. The highest CH incidence was observed in the Vardar region (1/970), while the Eastern region had the lowest incidence (1/4202; p=0.021). In the other regions, the following CH incidence was detected: Northeastern 1/1459, Pelagonia 1/1627, Polog 1/1444, Skopje 1/2430, Southwestern 1/3226, and Southeastern 1/1843. Interestingly, in the Vardar region, 4.44% of the screened newborns had a TSH concentration > 5 mIU/L, as an indicator of regional iodine deficiency, compared to the Eastern region where 1.66% of newborns had a TSH > 5 mIU/L. The higher CH incidence in some of the regions may be due to increasing exposure to environmental toxic agents and/or deficient iodine intake. Further research into the potential environmental determinants of increased CH risk is warranted.

Worldwide Recall Rate in Newborn Screening Programs for Congenital Hypothyroidism

CONTEXT

Neonatal mass screening program for congenital hypothyroidism provides the best tool for prevention of its devastating effects on mental development. Despite the overall success of the screening programs in detecting congenital hypothyroidism and eliminating its sequelae and new developments made in the program design, high recall rate and false positive results impose a great challenge worldwide. Lower recall rate and false positive results may properly organize project expenses by reducing the unnecessary repeated laboratory tests, increase physicians and parents' assurance and cooperation, as well as reduce the psychological effects in families.

EVIDENCE ACQUISITION

In this review, we assessed the recall rate in different programs and its risk factors worldwide.

METHODS

Publications reporting the results of the CH screening program from 1997 to 2016 focusing on the recall rate have been searched.

RESULTS

Recall rates vary from 0.01% to 13.3% in different programs; this wide range may be due to different protocols of screening (use of T4 or TSH or both), different laboratory techniques, site of sample collection, recall cutoff, iodine status, human error, and even CH incidence as affected by social, cultural, and regional factors of the population.

CONCLUSIONS

It is suggested to implement suitable interventions to reduce the contributing factors by improving the quality of laboratory tests, selecting conservative cut off points, control iodine deficiency, use of iodine free antiseptic during delivery, and use of more specific markers or molecular tests. Applying an age dependent criteria for thyrotropin levels can be helpful in regions with a varied time of discharge after delivery or for preterm babies.

Ethnicity and incidence of congenital hypothyroidism in the capital of Macedonia

BACKGROUND

Congenital hypothyroidism (CH) is a common and preventable cause of intellectual disability for which early diagnosis is difficult without newborn screening. Genetic and environmental factors, race, ethnicity, sex, and pregnancy outcomes were noted as risk factors. In the study we aimed to determine the incidence of CH among different ethnic groups in the capital of Macedoina - a multiethnic city.

METHODS

A 14-year retrospective cohort analysis was performed on 121,507 newborns in the capital of Macedonia, Skopje, screened for whole-blood thyroid-stimulating hormone (TSH), in dry blood spots collected 48-72 h after birth, during the period 2002-2015. A TSH value of 15 mIU/L was used as cutoff point until 2010 and 10 mIU/L thereafter.

RESULTS

Primary CH was detected in 46 newborns (female to male ratio 1.3) with overall incidence of 3.8/10,000 (1/2641). The incidence of primary CH was significantly increased after lowering the TSH cutoff value (p=0.038), primarily due to detected neonates with transient CH for this period. Ethnic differences in the incidence of primary CH were detected. CH incidence among Roma neonates (6.7/10,000) was significantly higher (p<0.05) than the incidence detected in Macedonians (3.9/10,000) or Albanians (3.7/10,000).

CONCLUSIONS

Increased incidence of CH in Roma newborns was detected as compared to other ethnicities in the capital of Macedonia. Further analysis of factors in direct interrelationship with the increased CH incidence in Roma newborns, as well as elucidation of impact of the CH incidence in this ethnicity on the overall incidence in Skopje, is warranted.

Newborn Screening for Thyroid-stimulating Hormone as an Indicator for Assessment of Iodine Status in the Republic of Macedonia

BACKGROUND

Iodine deficiency is associated with goiter and impaired brain function leading to cretinism. An increased frequency of thyroid-stimulating hormone (TSH) measurements above 5 mlU/L on newborn screening points toward an impaired iodine status of the population.

METHODS

A 13-year retrospective analysis was performed in 228,266 newborns participating in the national thyroid newborn screening program. The TSH concentration was measured in dry blood spots collected by heel stick on filter paper, 48 hours after birth, using fluoroimmunometric DELFIA method.

RESULTS

Out of 236,378 live-born infants, 228,266 (96.6%) have been screened for TSH, of which 198,213 (86.8%) were retrospectively evaluated for TSH levels above 5 mlU/L. Neonates with congenital hypothyroidism, prematurity, and low birth weight were excluded from the evaluation, as well as the inadequately sampled neonates (13.2%). A national prevalence of 3.08% newborns (n=6,105) with TSH > 5 mIU/L was found. Higher percentages were noted in two regions of the country, indicating possible mild iodine deficiency in these regions and shifting the overall average to above 3%.

CONCLUSIONS

Our results indicate overall iodine sufficiency in the Macedonian population. Additional assessment of the iodine intake in the regions with suspected mild iodine deficiency is needed to prevent suboptimal cognitive and psychomotor outcomes.

Frequency of thyroid status monitoring in the first year of life and predictors for more frequent monitoring in infants with congenital hypothyroidism

BACKGROUND

The essential role of thyroid hormones for normal brain development during a critical period of life is well established. Neonatal screening programs for congenital hypothyroidism (CH) enable early detection of patients and attainment of euthyroid status as quickly as possible. Adequate and accurate monitoring of thyroid function is necessary. In the study we aimed to determine the periodicity of thyroid function testing in the first year of life (3-month intervals versus <3-month intervals monitoring).

METHODS

We retrospectively analyzed charts of CH children from Macedonia detected on neonatal screening during a 3-year period (2011-2014). Needs for monthly thyroid monitoring were defined according to the recommendations: a dose change within a month of a previous control, values of T4/FT4 not in the upper half of the reference range, and a high or very low thyroid-stimulating hormone (TSH) value.

RESULTS

Monthly thyroid testing was indicated in more than a third of CH patients during the first year of life. Children who needed more frequent monitoring intervals had a higher initial value of TSH (p=0.032) and a lower value of T4 (p=0.038) than those requiring less frequent monitoring. The sex, birth weight, age of treatment onset, initial L-thyroxine dose, and L-thyroxine dose at 1-year of age in our study were not predictive factors for more frequent thyroid monitoring.

CONCLUSIONS

Children with severe hypothyroidism at birth are potential candidates for more frequent thyroid monitoring during the first year of life, although the individual patient approach should not be avoided as variations in TSH values are very common.

Newborn screening for congenital hypothyroidism in Henan province, China

BACKGROUND

Congenital hypothyroidism is the most common congenital endocrine disorder. The study aimed to determine the congenital hypothyroidism incidence by newborn screening programs in Henan Province, China.

METHODS

The screening programs for congenital hypothyroidism are based on the measurement of TSH in dried blood spots. The TSH concentration was measured in the dry blood spot specimen using a DELFIA fluoroimmunoassay. The TSH cutoff concentration was 8mU/l.

RESULTS

The total coverage and the incidence of congenital hypothyroidism were 24.85% (5,142,148/20,694,441) and 0.37‰ (1992/5,142,148), respectively. The coverage and the incidence of CH were only 0.58% (4526/784,580) and 0.22‰ (1/4526) in 1997, respectively. However, the coverage and the incidence of CH were increased to 74.67% (1,203,278/1,611,582) and 0.32‰ (389/1,203,278). There were no significant differences in the number of congenital hypothyroidism between males and females (P>0.05). The number of congenital hypothyroidism was increased year after year.

CONCLUSIONS

The newborn screening program for CH is successful and quite effective.