Investigation of TSH levels during the 3- 5th days of birth in term and pre-term infants

doi:10.21203/rs.3.rs-2356307/v1

Introduction: Congenital hypothyroidism (CH) is one of the most common causes of hormonal disorders and can be detected through timely screening in new-borns. The present study was conducted with the aim of investigating TSH levels 3- 5th days after birth in term and pre-term infants.

Materials and Methods: This cross-sectional descriptive study was conducted on all live new born babies in Shahroud City 3- 5th days after birth in 2021. From these infants, four - five drops of blood were collected from the heel of the foot and dripped on a special filter paper and TSH levels were measured.

Results: In this study, 2498 infants were examined and their TSH levels were recorded four times during CH screening. 1291 (51.7%) people were boys and the rest were girls. Of these, 2353 (94.2%) were full-term babies and the rest were pre-term babies. In the first screening, the TSH level was >20 mu/lit in 142 (5.7%) babies and between 10 and 20 mu/lit in 74 (3%) babies. In the second round of screening, TSH levels were measured in 548 babies, and only 6 babies (1.1%) had TSH levels greater than 10 mu/lit. In the third screening, TSH levels were measured in 94 babies, and in 18 babies (19.1%), TSH levels between 4 and 10 mu/lit were reported. Finally, in the fourth screening, TSH levels were measured in 69 babies, but only in 18 babies (26.1%); it was between 4 and 10 mu/lit.

Conclusion: The results of the present study showed that the prevalence of CH in 3 to 5 day old infants in Shahroud City was approximately 16%, and no significant difference was seen between term and pre-term babies. However, it is necessary that in babies whose values have abnormal TSH, screening must be performed in the next appointments.

Congenital Hypothyroidism

Screening

Term baby

Pre-term baby

CH is defined as lack of thyroid hormone at birth. Thyroid hormone plays an essential role in energy metabolism, growth and neural development (1). Specifically, thyroid hormone acts in neuronal differentiation, synapses growth, and myelination of neurons in the prenatal and neonatal periods and regulates the development of the central nervous system (1-2). CH may have a thyroid or central origin, which is called primary and central congenital hypothyroidism, respectively. The majority of CH is caused by thyroid dysgenesis (80%), which includes a variety of defects such as agenesis of the thyroid gland, ectopic thyroid gland, or hypoplastic thyroid gland (4). While some defects cause permanent CH, some conditions may be transient (5). Among these conditions, the passage of maternal anti-thyroid drugs (methimazole or propylthiouracil) through the placenta, maternal thyroid-blocking antibodies (in a mother with autoimmune thyroid disease) or iodine deficiency can be mentioned (5-8).

The range of prevalence of CH in the world varies from 14.7 cases per 1000 live births in Nigeria (5) to 0.14 cases per 1000 live births in Japan (6), but the overall prevalence of CH is occurs from in 1 cases 3,000 to 1 in 4,000 live births (7). The prevalence of this disease among female babies is about 1.5 to 2 times higher. Also, in twins and multiple births, older mothers and premature babies are more common (8-10). The prevalence of CH is also different in different parts of Iran, such that its rate is 1 case in every 914 live births in Tehran (11), 1 case in every 1465 live births in Fars (12) and 1 case in every 342 live births in Isfahan (13).

In infants with primary CH, hypothyroidism usually causes a decrease in the level of T4 and T3, which is associated with high levels of TSH and TRH following the feedback mechanism of thyroid hormones on the hypothalamus and pituitary gland (14).

Most infants with CH have no clinical manifestations or mild symptoms at birth. This factor is due to the partial transfer of the mother's thyroxine hormone (about 25 to 50 percent). The classic clinical features of CH appear gradually over approximately six weeks, but in more severe cases, initial symptoms may appear within the first few weeks of life (15). Early manifestations include lethargy, hypotonia, large anterior and posterior fontanelles, difficulty feeding, prolonged jaundice, weak or harsh crying, constipation, and hypothermia (16). Classic late manifestations of CH usually occur after about six weeks of life. These include a rough appearance with an abnormal nasal bridge, puffy eyelids, large tongue, coarse hair, thick and dry skin, abdominal distension, umbilical hernia, hyporeflexia, bradycardia, hypotension, and anemia. Since infants with CH are often asymptomatic at birth, their disorder is diagnosed through screening (17-18). Newborn screening is done through dried heel blood samples on filter paper cards. Screening priority is early detection of primary CH. The most specific test to diagnose primary CH is TSH measurement, while the T4 test is more sensitive because it also includes infants with rare hypothalamic-pituitary-hypothyroidism (19). Newborn screening for CH should ideally be done between days 2 and 4 after birth. The screening program for congenital hypothyroidism is important both in order to preserve the human capital of the society and economically, because the maintenance and treatment of patients and the complications caused by hypothyroidism and mental retardation are estimated to be far more than the cost of screening (19-20). In the last 40 years, screening for CH has been able to prevent mental disabilities in many sufferers and reduce the socio-economic burden of the disease (21).Considering the importance of the subject, the present study was conducted with the aim of determining the TSH level during the 3- 5th days of birth in term and pre-term infants in Shahroud city in 2021.

The current research was a cross-sectional descriptive and analytical study. The target population was all live babies born in 2021 in Shahroud city who were referred on the 3- 5th day after birth. From all eligible babies, 4 to 5 drops of heel blood samples were taken by auto lancet and dripped on a special filter paper, and the TSH level was measured and recorded. Also, information such as gender, gestational age, and birth weight, history of hospitalization, twins or multiples, and the use of special medications by the mother during pregnancy were also recorded for each baby. The results were also recorded in the babies who were screened for the second time. Also, in premature babies, the third and fourth screenings were also recorded.

The best way to screen for CH is the simultaneous measurement of TSH and T4 (1-3), which can show primary disorders of the thyroid, pituitary, and hypothalamus (4). In the present study, due to the national screening protocol for CH and lack of funds, only TSH was measured.

Primary CH may be masked by suppression of TSH secretion due to hypothalamic-pituitary immaturity, drug administration, and the effects of serious neonatal diseases. Delayed increase of TSH (means increase of TSH in the second newborn screening after normal TSH in the initial screening) is observed in half of premature babies (20). The second screening is recommended by the European and American pediatric societies for infants with low birth weight, gestational age less than 37 weeks, and sick infants admitted to the neonatal intensive care unit (NICU) (21). Screening protocols for premature babies include measurements on days 3 to 5 and in the first week, second week, fourth week and the day of discharge from the hospital (20- 22). Also, a TSH level of 10 mU/L or more is considered positive for CH (23). Data were analyzed by descriptive statistics in SPSS ver. 16.

In the present study, 2498 infants were examined, of which 1291 (51.7%) were boys and 1207 (48.3%) were girls. 2353 people (94.2%) were full-term babies and the rest were pre-term babies. Also, 2370 people (94.9%) of the babies had normal weight (2500 to 4000 grams). The demographic and clinical information of the newborns is presented in Table 1.

In the first screening, TSH levels were measured for all newborns, which were normal (<5 MU/L) in 2095 (86.8%) and abnormal (> 5 MU/L) in 403 (2.14%) babies. As can be seen, gender (P= 0.020) and history of hospitalization (P= 0.001) have a significant difference with the TSH level. The results of the first measurement of TSH levels by variables are shown in Table 2.

All premature babies and full-term babies, whose number in the level of TSH in the first appointment was more than 4MU/L (548 people), were examined for the second round of screening. The results of the second measurement of TSH levels by variables are shown in Table 3.

Again all babies, whose number in the level of TSH in the second appointment was more than 4MU/L (94 people), were examined for the third round of screening. As can be seen, gender (P= 0.019) has a significant difference with the TSH level. The results of the third measurement of TSH levels by variables are shown in Table 4.

Again for the fourth time, all babies, whose number in the level of TSH in the third appointment was more than 4MU/L (69 people), were examined for the fourth round of screening. As can be seen, gestational age (P= 0.012) has a significant difference with the TSH level. The results of the third measurement of TSH levels by variables are shown in Table 5.

The results of the present study showed that the abnormal level of TSH during screening was 16.1%, 8.2%, 19.2%, and 26.1% during the first to fourth rounds, respectively. In a study conducted by Nasehi et al., in Mazandaran province in 2012, it was seen that 16. 6% of the newborns in the first TSH screening test had TSH above 5 milliunits/liter that for specifically, they were recalled again (24).

Our study showed that there was a significant difference between the gender of infants in TSH screening in the first time (P = 0.020) and the third time (P = 0.019), so that these disorders were significantly higher in female infants. In the study of Feleke et al., the mean TSH level in hypothyroid girls was higher than that of boys (25). Also, in their study, Medda et al., found a significant relationship between female gender and the increase in the prevalence of hypothyroidism (26). But in other reviewed studies, despite the gender superiority of girls in the occurrence of CH, this relationship was not statistically significant (27–30).

In the present study, it was found that the positive history of hospitalization of the newborn can be significantly related to the increase of TSH level in the first screening of congenital hypothyroidism (P = 0.001). In the study of Asadi Karmi et al., a significant relationship was observed with thyroid dysfunction (CH) and hospitalization of the baby (31), but in the study of Henry et al., and Helfrick et al., such a relationship was not found which contradicts with our study that perhaps the most important causes of this difference are related to the method of diagnosing CH, the method of TSH measurement and also the difference in the sample size of the above two studies (32–33).

In our study, there was no significant relationship between the weight of newborns and TSH level in all 4 times of screening. In Ghafarpour Sakha et al., study hypothyroidism decreased with high weight in premature babies (high FT4 and low TSH) and hypothyroidism was more likely with weight loss (34).

In the studies of Mao et al., Tylek-Lemańska et al., and Waller et al., an increase in the prevalence of CH was seen in low birth weight infants, but this increase was not statistically significant (35–37).

In the present study, no significant relationship was found between gestational age and TSH level in all 4 screening times. Studies by Henry et al., and Waller et al., also reached similar results to ours (32, 37). In the study of Asadi Karmi et al., it was seen that the more premature the baby, the more likely CH is (31). Also, Mao et al., showed a higher prevalence of congenital hypothyroidism in preterm and post term infants (35). Medda et al., and Kurinczuk et al., also showed an increase in the prevalence of CH with a gestational age of more than 40 weeks, which was statistically significant (26, 38).

Finally, the results of the present study showed that the prevalence of congenital hypothyroidism in 3- to 5-day-old infants in Shahroud city was about 16%, and it is necessary to measure TSH in the appointments for more accurate diagnosis of congenital hypothyroidism, especially for preterm infants, it will be done for babies.

Limitation

One of the limitations of the present study is the lack of measurement of F4 due to the lack of funds, as well as the lack of full cooperation of parents to follow up for tests and screening at different stages. It is hoped that more comprehensive research will be planned and implemented in future studies after solving the above problems.

CH: Congenital Hypothyroidism

Mu/lit: MiliUnit/ liter

SPSS: Statistical Package for Social Science

- Ethics approval and consent to participate

All authors of this article confirm that all relevant experiments were performed in accordance with relevant research guidelines and regulations. This study was reviewed and approved by Ethical Board of Shahroud University of Medical Sciences (IR.SHMU.REC.1400.162). Also, all the measures taken and especially the tests taken have been done under the supervision and approval of the ethics committee of Shahroud University of Medical Sciences. Informed consent was obtained from all individual participants who participated in the study or their legal guardians (parents) using a standardized form.

- Consent for publication

Not applicable

- Availability of data and material

The dataset used and/or analyzed during the present study is available from the corresponding author upon reasonable request.

Competing interests

The authors declared that they have no conflict of interest.

- Funding

This study received funding from the research deputy of Shahroud University of Medical Sciences.

- Authors’ contributions: MH.K., MB.S., and K.J. designed the study. MH.K., A.T. and P.Z. collected the data. Drafting the manuscript was done by MB.S., MH.K., K.J., and A.T. All authors read and approved the final version to publishing and agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work.

- Acknowledgment

The present study was supported by Shahroud University of Medical Sciences as a Medical Doctor (MD) Thesis (number code: 1062). We hereby acknowledge the research deputy. Also, we would like to thank all participated patients.

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Table 1. The demographic and clinical information of the new borne variation of TSH level

Variable	Number (%)
Sex
Male	1291 (51.7)
Female	1207 (48.3)
Gestational age
Term (>36 w)	2353 (94.2)
Preterm (>36w)	145 (5.8)
Birth weight
Normal (2500-4000g)	2370 (94.9)
Low birth weight (<2500g)	95 (3.8)
High birth weight (>4000g)	33 (1.3)
Multiple births
Singleton	2436 (97.5)
Twins or more	62 (2.5)
Type of delivery
Normal (Vaginal)	1687 (67.5)
Cesarean section	1211 (32.5)
Hospitalization of the baby
Positive	429 (17.2)
Negative	2069 (82.8)
Mother's age at delivery
18-35 years	1504 (60.2)
<18 years	287 (11.5)
>35 years	707 (28.3)

Table 2: Checking the level of TSH in the first appointment by background variables

p-value

Total

Number (%)

>20 MU/L

Number (%)

10-20 MU/L

Number (%)

4-10 MU/L

Number (%)

<4 MU/L

Number (%)

TSH level

0.020

1291(51.7)

1207 (48.3)

44 (59.5)

30 (40.5)

89 (62.7)

53 (37.3)

99 (52.9)

88 (47.1)

1059 (50.5)

1036 (49.5)

Sex

Male

Female

0.829

2353 (94.2)

145 (5.8)

68 (91.9)

6 (8.1)

133 (93.7)

9 (6.3)

177 (94.7)

10 (5.4)

1975 (94.3)

120 (5.7)

Gestational age

Term

Pre-term

0.675

95 (3.8)

2370 (94.9)

33 (1.3)

4 (5.4)

70 (94.6)

0 (0.0)

8 (5.6)

133 (93.7)

1 (0.7)

5 (2.8)

179 (95.7)

3 (1.6)

78 (3.7)

1988 (94.9)

29 (1.4)

Birth weight

Low

Normal

High

0.001

2069 (82.8)

429 (17.2)

55 (74.3)

19 (25.7)

102 (71.8)

40 (28.1)

138 (73.8)

49 (26.2)

1774 (84.7)

321 (15.3)

Hospitalization

Negative

Positive

0.815

2436 (97.5)

62 (2.5)

71 (95.9)

3 (4.1)

139 (97.9)

3 (2.1)

183 (97.9)

4 (2.1)

2043 (97.5)

51 (2.5)

Multiple births

Singleton

Twins or more

Table 3: Checking the level of TSH in the second appointment by background variables

p-value

Total

Number (%)

10-20 MU/L

Number (%)

4-10 MU/L

Number (%)

<4 MU/L

Number (%)

TSH level

0.476

312 (56.9)

236 (43.1)

4 (66.7)

2 (33.3)

21 (53.8)

18 (46.2)

287 (57.1)

216 (42.9)

Sex

Male

Female

0.880

481 (87.8)

67 (12.2)

5 (83.3)

1 (16.7)

35 (89.7)

4 (10.3)

441 (87.7)

62 (12.3)

Gestational age

Term

Pre-term

0.841

55 (10.1)

473 (86.3)

20 (3.6)

0 (0)

6 (100.0)

0 (0.0)

5 (12.8)

33 (84.6)

1 (2.6)

50 (9.9)

434 (86.3)

19 (3.8)

Birth weight

Low

Normal

High

0.297

187 (34.1)

361 (65.9)

1 (16.7)

5 (83.3)

17 (43.6)

22 (66.4)

169 (33.6)

334 (66.4)

Hospitalization

Negative

Positive

0.371

517 (94.3)

31 (5.7)

6 (100.0)

0 (0.0)

35 (89.7)

4 (10.3)

476 (94.6)

27 (5.4)

Multiple births

Singleton

Twins or more

Table 4: Checking the level of TSH in the third appointment by background variables

p-value

Total

Number (%)

4-10 MU/L

Number (%)

<4 MU/L

Number (%)

TSH level

0.019

49 (52.1)

45 (47.9)

14 (77.8)

4 (22.2)

35 (46.1)

41 (53.9)

Sex

Male

Female

0.255

85 (90.4)

9 (9.6)

15 (83.3)

3 (16.7)

70 (92.1)

6 (7.9)

Gestational age

Term

Pre-term

0.262

30 (31.9)

64 (68.1)

0 (0.0)

8 (44.5)

10 (55.6)

0 (0.0)

22 (28.9)

54 (71.1)

0 (0.0)

Birth weight

Low

Normal

High

0.604

37 (39.4)

57 (60.6)

6 (33.3)

12 (66.7)

31 (40.8)

45 (59.2)

Hospitalization

Negative

Positive

0.123

75 (79.8)

19 (20.2)

12 (66.7)

6 (33.3)

63 (82.9)

13 (17.1)

Multiple births

Singleton

Twins or more

Table 5: Checking the level of TSH in the fourth appointment by background variables

p-value

Total

Number (%)

4-10 MU/L

Number (%)

<4 MU/L

Number (%)

TSH level

0.177

40 (57.9)

29 (42.1)

13 (72.2)

5 (37.8)

27 (52.9)

24 (47.1)

Sex

Male

Female

0.012

3 (4.3)

66 (95.7)

2 (11.1)

16 (88.9)

1 (1.9)

50 (98.1)

Gestational age

Term

Pre-term

0.262

26 (37.7)

43 (62.3)

0 (0.0)

9 (50.0)

0 (0.0)

17 (33.3)

34 (66.7)

0 (0.0)

Birth weight

Low

Normal

High

0.569

25 (36.2)

44 (63.8)

5 (37.8)

13 (72.2)

20 (39.2)

31 (60.8)

Hospitalization

Negative

Positive

0.784

56 (81.2)

13 (18.8)

15 (83.3)

3 (16.7)

41 (80.4)

10 (19.6)

Multiple births

Singleton

Twins or more

No competing interests reported.

Investigation of TSH levels during the 3- 5th days of birth in term and pre-term infants

Status:

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Abstract

Introduction

Materials & Methods

Results

Discussion

Conclusion

Abbreviations

Declarations

References

Tables

Additional Declarations

Status:

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