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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 33  |  Issue : 3  |  Page : 878-881

Free thyroxine and thyroid-stimulating hormone in preterm neonates with respiratory distress syndrome


1 Department of Pediatric, Faculty of Medicine, Menoufia University, Menoufia, Egypt
2 Department of Neonatology, Samanoud General Hospital, Gharbia, Egypt

Date of Submission14-Jan-2019
Date of Decision28-Feb-2019
Date of Acceptance02-Mar-2019
Date of Web Publication30-Sep-2020

Correspondence Address:
Asmaa A. M. M. Zidan
El Mahalla, Gharbia
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/mmj.mmj_440_18

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  Abstract 


Objective
To study the level of serum free tetraiodothyronine (FT4) and thyroid-stimulating hormone (TSH) in cases of respiratory distress syndrome (RDS) in preterm neonates and its correlation with other clinical findings.
Background
RDS is one of the most common respiratory complications of prematurity. The relationship between RDS and thyroid hormones levels was the target of this study.
Patients and methods
This was a case-control study that included 90 preterm neonates (60 preterm neonates with RDS and 30 healthy preterm neonates with matched gestational age and sex as controls), conducted in the neonatal ICU, Menoufia University Hospital, Egypt, from October 2017 to September 2018.
Results
Mean value of serum FT4 was statistically significant lower among cases than controls, whereas serum TSH was statistically significant higher among cases than controls. There were statistically significant positive correlations between serum FT4 and gestational age, New Ballard score, weight, Apgar score at 1 min, and Apgar score at 5 min, whereas statistically significant negative correlation between FT4 and Downes score. There were statistically significant positive correlations between serum TSH and Downes score, whereas there were statistically significant negative correlations between serum TSH and gestational age, New Ballard score, weight, Apgar score at 1 min, and Apgar score at 5 min.
Conclusion
The present study showed that there was a negative significant correlation between serum FT4 level and the occurrence and severity of RDS, and there was a positive significant correlation between serum TSH level and the occurrence and severity of RDS.

Keywords: free thyroxine, neonates, prematurity, respiratory distress syndrome, surfactant and thyroid-stimulating hormone


How to cite this article:
Tawfik MA, El Gendy FM, Zidan AA. Free thyroxine and thyroid-stimulating hormone in preterm neonates with respiratory distress syndrome. Menoufia Med J 2020;33:878-81

How to cite this URL:
Tawfik MA, El Gendy FM, Zidan AA. Free thyroxine and thyroid-stimulating hormone in preterm neonates with respiratory distress syndrome. Menoufia Med J [serial online] 2020 [cited 2020 Oct 20];33:878-81. Available from: http://www.mmj.eg.net/text.asp?2020/33/3/878/296696




  Introduction Top


Respiratory distress syndrome (RDS) is one of the most common respiratory complications of prematurity. Its incidence is inversely related to gestational age and birth weight. It occurs in 60–80% of infants less than 28 weeks of gestational age, in 15–30% those between 32 and 36 weeks of gestational age, and rarely occurs in those more than 37 weeks of gestational age [1].

The clinical presentation of respiratory distress in the form of tachypnea, expiratory grunting, subcostal and intercostal retractions, nasal flaring, and cyanosis usually manifests in the first few hours and almost always before 8 h of age. If symptoms do not develop until after 8 h of age, RDS is excluded. On auscultation, there is diminished air entry despite vigorous respiratory effort [2].

The diagnosis of RDS is based on a combination of the previously described clinical signs, evidence of prematurity, excluding other causes of respiratory distress, and the classic radiologic appearance of diffuse reticulogranular pattern, air bronchogram, and low-volume lungs [3].

Thyroid dysfunction is common among preterm infants [4]. The incidence of congenital hypothyroidism (CH) with delayed thyroid-stimulation hormone (TSH) elevation as high as one in 11 is reported in some studies [5].

The aim of the work was to study the level of serum free tetraiodothyronine (FT4) and TSH in cases of RDS in preterm neonates and its correlation with other clinical findings.


  Patients and Methods Top


This is a case-control study, which was conducted in the neonatal ICU, Faculty of Medicine, Menoufia University Hospital. This study conducted on 90 preterm neonates (age of neonates >28 weeks and <37 weeks). Newborn included in the study were divided into two groups: group 1 (case group I) included 60 preterm neonates with RDS, and group 2 (control group II) included 30 healthy preterm neonates with matched gestational age and sex as controls. Samples were obtained from first to seventh day of life from October 2017 to September 2018. Informed consents were obtained from all patient guardians. The study was approved by Ethical Committee of Menoufia University.

The inclusion criteria were patients aged more than or equal to 28 weeks and less than 37 weeks (preterm neonates) with RDS clinical signs shortly after birth. These included tachypnea, nasal flaring, retractions, grunting, and cyanosis. Respiratory distress was evaluated by Downes score, where score 4 means no respiratory distress, scores 4–7 mean respiratory distress, and score 7 means impending respiratory failure; blood gases are required; and the classic radiographic appearance is of low-volume lungs with diffuse reticulogranular pattern and air bronchograms. The diagnosis of RDS is based on a combination of the clinical features (tachypnea, subcostal, intercostal retractions, nasal flaring, and cyanosis; on auscultation, air movement is diminished despite vigorous respiratory effort), evidence of prematurity, and exclusion of other causes of respiratory distress [6].

Exclusion criteria for the patients were if they had congenital defects, sepsis, maternal thyroid diseases, and maternal drug abuse.

All neonates were subjected to detailed history, which included history taking from the mother, laying stress on gestational age at delivery; antenatal history, stressing on history of preeclampsia, diabetes mellitus, fever, and infections; natal history, included mode of delivery, fever, offensive liquor, vaginal discharge, premature rupture of membrane, and aspiration; and postnatal history, including fever, hypothermia, convulsions, jaundice, and respiratory distress.

Neonatal clinical examination was done for confirmation of estimated gestational age of the neonate using New Ballard score. General examination included vital signs, colors, and anthropometric measurement. Systems' examination included neurological examination (anterior fontanel, head circumference, fits, and reflexes), cardiac examination (heart sounds and murmur), chest examination (air entry and adventitious sound), abdominal examination (contour and organomegaly), and external genitalia (congenital anomalies).

Laboratory investigations included complete blood count, with differential count done by coulter T660, CRP measured by latex agglutination test, arterial blood gas done by ABL 800 from Kent Company (Willesborough, England), serum FT4 assayed on Immolate 2000 (FT4 is a solid-phase enzyme-labeled chemiluminescent competitive immunoassay), and TSH measured by Immulite 2000 third generation. Radiological investigation included chest radiography.

Statistical analysis

Data were collected, tabulated, and statistically analyzed using a personal computer with statistical package of the social science, version 20, for Windows (SPSS Inc., Chicago, Illinois, USA). Data were expressed as mean ± SD. Student's t test was used to assess the difference between the studied parameters in the two groups. The frequencies were expressed in %. χ2 was used to assess the difference between the studied frequencies in the two groups. Correlation coefficient (r) was used to evaluate the relation between the studied parameters in the same group. P value was considered significant if less than 0.05 and highly significant if less than 0.001.


  Results Top


There was no statistically significant difference between cases and controls regarding demographic data [Table 1].
Table 1: Demographic data of all cases and controls

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There was no statistically significant difference between cases and controls regarding New Ballard score. There was a statistically significant difference between cases and controls regarding Downes score, Apgar score at 1 min, and Apgar score at 5 min [Table 2].
Table 2: Clinical assessment of all cases and controls

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There was a statistically significant difference between cases and controls regarding FT4 and TSH [Table 3].
Table 3: Free tetraiodothyronine and thyroid-stimulating hormone of cases and control

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There were statistically significant positive correlations between FT4 and gestational age, New Ballard score, weight, Apgar score at 1 min, and Apgar score at 5 min. There was a statistically significant negative correlation between FT4 and Downes score. There were no statistically significant correlations between FT4 level and other variables [Table 4].
Table 4: Correlation between free tetraiodothyronine and other numerical data

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There were statistically significant positive correlation between TSH and Downes score, whereas there were statistically significant negative correlations between TSH and gestational age, New Ballard score, weight, Apgar score at 1 min, and Apgar score at 5 min. There were no statistically significant correlations between TSH and age [Table 5].
Table 5: Correlation between thyroid-stimulating hormone and other numerical data

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  Discussion Top


This study showed that there was no statistically significant difference between cases and controls regarding demographic data. This can be explained as the inclusion criteria of the control group was to be matched with the case group regarding age and sex.

The present study revealed that RDS preterm neonates had lower Apgar score at both 1 min and 5 min than the normal preterm neonates. This coincides with the study done by Chandrasekhar et al. [7], on 100 preterm neonates with respiratory distress, which revealed that 1 min Apgar score less than 7 is a risk factor for RDS. Moreover, Patil et al. [8] denoted that 53% of newborns with 1 min Apgar of less than 7 developed severe respiratory distress compared with 36% with 1 min Apgar more than 7.

Moreover, this agrees with Liu and Tong [9], who conducted a study on 99 preterm infants (69 neonates were diagnosed with TTN and 30 were diagnosed with RDS), with mean gestational age of 31.9 ± 2.2 weeks and birth weight of 1661 ± 501 g, and revealed lower Apgar score in RDS group (nine cases in the RDS group had Apgar score ≤7, whereas four cases in the TTN group had Apgar score ≤7) (P = 0.001).

This study showed that the mean value of FT4 was statistically significant lower among cases than controls.

This is in accordance with the findings of El Mazahy et al. [10], which showed that the FT4 was significantly decreased in RDS preterm neonates more than that in healthy normal ones (P < 0.050).

Moreover, the results of our study revealed that there was significant correlation between TSH and the severity of RDS (respiratory clinical picture based on Downes score, but there was significant negative correlation between FT4 and Downes score). In keeping with our study, the study done by Dilli et al. [11], on 200 infants (26–32 weeks gestation) admitted to neonatal ICUs – when adjusted for age, transient hypothyroxinemia of prematurity was associated with need for mechanical ventilation (P = 0.03) and for having RDS.

A previous study revealed the relationship between FT4 and TSH levels and RDS in preterm infants during first postnatal day which is in accordance with the fact that thyroid hormones play a role in surfactant synthesis, and this does support the idea that deficiency of thyroid hormones leads to occurrence of RDS. It also supports the idea that hypoxia from RDS affects hypothalamic–pituitary–thyroid axis and hence lowers thyroid hormone levels [10].

The difference between the present study and others regarding FT4 and TSH levels may be owing to differences in gestational ages, which contributes to this difference, and also the variation of the methods of hormonal assay.

This study showed a positive correlation between FT4 and both birth weight and gestational age. Moreover, this study showed a statistically significant negative correlation between TSH and both birth weight and gestational age.

Similarly, Wang et al. [12] observed lower levels of TSH and a higher incidence of CH in premature neonates relative to full-term neonates.

Low-birth-weight neonates also had lower TSH levels, compared with normal-birth-weight and high-birth-weight neonates. Primary screening for CH might not be able to identify neonates with delayed rise in TSH, and a recent guideline recommended repeating screening in premature and low-birth-weight neonates [13].


  Conclusion Top


The present study showed that there was a negative significant correlation between serum FT4 level and the occurrence and severity of RDS, and there was a positive significant correlation between serum TSH level and the occurrence and severity of RDS. So thyroid hormones affect occurrence and severity of RDS.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Reuter S, Moser C, Baack M. Respiratory distress in the newborn. Pediatr Rev 2014; 35:417–428.  Back to cited text no. 1
    
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Wong JJ, Quek BH, Lee JH. Establishing the entity of neonatal acute respiratory distress syndrome. J Thorac Dis 2017; 9:4244–4247.  Back to cited text no. 2
    
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Liu J, Cao HY, Wang HW. The role of lung ultrasound in diagnosis of respiratory distress syndrome in newborn infants. Iran J Pediatr 2014; 24:147–154.  Back to cited text no. 3
    
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Kaluarachchi D, Colaizy T, Pesce L, Tansey M, Klein J. Thyroid dysfunction in very low birth weight premature infants. J Perinatol 2017; 37:277–282.  Back to cited text no. 4
    
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Lee JH, Kim SW, Jeon GW, Sin JB. Thyroid dysfunction in very low birth weight preterm infants. Korean J Pediatr. 2015;58:224–229.  Back to cited text no. 5
    
6.
Liu J, Shi Y, Dong JY, Zheng T, Li JY, Lu LL, et al. Clinical characteristics, diagnosis and management of respiratory distress syndrome in full-term neonates. Chin Med J 2010; 123:2640–2644.  Back to cited text no. 6
    
7.
Chandrasekhar R, Mohan MM, Lakshmi BV. Clinical study of respiratory distress in newborn. Int J Contem Pediatr 2016; 3:910–915.  Back to cited text no. 7
    
8.
Patil S, Halkude V, Tondare M, Mudaglimath A. Study of risk factors associated with development of severe respiratory distress in the new born. Int J Contemp Pediatr 2018; 5:2235–2239.  Back to cited text no. 8
    
9.
Liu S, Tong X. The clinical comparative study of preterm respiratory distress syndrome and transient tachypnea of newborn. Zhonghua Er Ke Za Zhi 2015; 53:104–108.  Back to cited text no. 9
    
10.
El Mazahy MM, Al Sehaimy LA, Salem MF, Hamad AMM. Relationship between serum free T4 and thyroid stimulating hormone levels in preterm neonates and respiratory distress syndrome. Nat Sci 2018; 16:84–95.  Back to cited text no. 10
    
11.
Dilli D, Oǧuz SS, Andiran N, Dilmen U, Büyükkaǧnici U. Serum thyroid hormone levels in preterm infants born before 33 weeks of gestation and association of transient hypothyroxinemia with postnatal characteristics. J Pediatr Endocrinol Metab 2010; 23:899–912.  Back to cited text no. 11
    
12.
Wang Y, He Y, Zhuang L, Li X, Chen T, Chen L, et al. Effect of maternal and neonatal factors on neonatal thyroid screening results. Clin Lab 2018; 64:1445–1450.  Back to cited text no. 12
    
13.
Léger J, Olivieri A, Donaldson M, Torresani T, Krude H, van Vliet G, et al. European Society for Paediatric Endocrinology Consensus Guidelines on screening, diagnosis, and management of congenital hypothyroidism; congenital hypothyroidism consensus conference group. Horm Res Paediatr 2014; 81:80–103.  Back to cited text no. 13
    



 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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