Thyroid function in healthy and unhealthy preterm newborns

Developmental Trends in Postnatal Thyroid Hormones and Thyroid Dysfunction in Preterm Infants Born at less than 34 weeks Gestation

OBJECTIVES

To analyse the trends in thyroid function tests (TFT) in preterm infants, evaluate the frequency of thyroid dysfunction, and identify the factors that influence thyroid function.

METHODS

The TFT results and risk factors for thyroid dysfunction in preterm infants with gestational ages (GA) between 25 and 34 weeks were analysed.

RESULTS

In total, 535 infants were enrolled in this study. Thyroid hormone levels vary with gestational and postnatal age, and the total frequency of thyroid dysfunction is 50.3%. Thirty-one infants (5.8%) had delayed TSH elevation. Transient hypothyroxinaemia of prematurity remained significantly associated with both lower birth weight and GA. Congenital hypothyroidism was significantly associated with lower birth weight, 5 min Apgar score, and dopamine use.

CONCLUSIONS

Thyroid hormone levels in preterm infants are related to gestation and postnatal age, the frequency of thyroid dysfunction in premature infants is high, and is negatively correlated with GA and birth weight.

Thyroid Dysfunction and the Effect of Iodine-Deficient Parenteral Nutrition in Very Low Birth Weight Infants: A Nationwide Analysis of a Korean Neonatal Network Database

Background: To investigate the impact of nutritional iodine deficiency on thyroid dysfunction (TD) in very low birth weight (VLBW) infants, we analyzed the association between iodine-deficient parenteral nutrition (PN) and TD requiring L-thyroxine (TD-LT4). Methods: Data of VLBW infants were obtained from the Korean Neonatal Network registry. Factors including duration of PN were analyzed according to TD-LT4. Results: TD-LT4 occurred in 490 (8.7%) of 5635 infants, and more frequently occurred in infants requiring PN for ≥4 weeks (10.2%). PN ≥ 4 weeks was one of the risk factors for TD-LT4, with an odds ratio (OR) of 1.346, p = 0.002. However, multivariate analysis showed that TD-LT4 was more of a risk for infants that were small for gestational age (OR 2.987, p < 0.001) and for other neonatal morbidities such as seizures (OR 1.787, p = 0.002) and persistent pulmonary hypertension (OR 1.501, p = 0.039) than PN ≥ 4 weeks (OR 0.791, p = 0.080). Conclusions: Prolonged iodine-deficient PN might affect TD-LT4 in VLBW infants. However, the effect of nutritional iodine deficiency on TD-LT4 risk was less than that of SGA or severe neonatal morbidities in Korean VLBW infants.

An analysis of perinatal factors of low T3 syndrome in preterm neonates with a gestational age of 28-35 weeks

OBJECTIVE

Low triiodothyronine syndrome (LT3S) is a common endocrine disease in preterm neonates. Various serious acute or chronic diseases result in LT3S. Few studies have investigated the causal relationship between perinatal factors and LT3S in preterm neonates with a gestational age (GA) of 28-35 weeks. The present study comprehensively analyzed the perinatal factors of LT3S in preterm neonates.

METHODS

This was a retrospective study of neonates with and without LT3S from January 2018 to November 2019. Compared to 206 preterm neonates without LT3S, 158 neonates were diagnosed with LT3S, excluding neonates with congenital malformations, other endocrine diseases, genetic diseases and inherited metabolic diseases.

RESULTS

Five perinatal risk factors for LT3S were confirmed using univariate and multivariate analyses: smaller gestational age, lower birth weight, respiratory distress syndrome (RDS), neonatal sepsis, and dopamine use.

CONCLUSIONS

LT3S in preterm neonates was associated with multiple perinatal factors, including smaller gestational age, lower birth weight, RDS, sepsis, and dopamine use. Preterm neonates with a GA of 28-35 weeks who are exposed to a series of high-risk perinatal factors must be closely observed, diagnosed early and treated for primary diseases promptly to reduce the occurrence of LT3S and improve the outcomes.Key Message:Few studies have investigated the relationship between perinatal factors and Low triiodothyronine syndrome (LT3S) in preterm neonates with a gestational age (GA) of 28-35 weeks.LT3S was associated with multiple perinatal factors, including smaller gestational age, lower birth weight, respiratory distress syndrome (RDS), sepsis, and dopamine use.

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.

Transient hypothyroxinemia of prematurity and its risk factors in an extramural neonatal intensive care unit

Objective

Thyroid functions in preterm newborns may be altered in the first week of life. Hypothyroxinemia has been commonly reported in these babies, which could be due to the immaturity of the hypothalamic pituitary thyroid axis or acute illness. It could have a long-term impact on the developing brain of these babies. We conducted this study to estimate the incidence of transient hypothyroxinemia of prematurity (THOP) and to determine its risk factors.

Methods

We analyzed thyroid stimulating hormone (TSH) and free T4 levels of 64 preterm neonates admitted in the neonatal intensive care unit. TSH and free T4 levels were measured in the first week and then at 14-21 days of life to estimate the incidence of THOP and determine its risk factors. We also estimated the incidence of congenital hypothyroidism (CH) and delayed TSH elevation in CH. Risk analysis was conducted using simple and multiple logistic regression, and numerical data was compared using the Mann Whitney U test and t test.

Results

THOP was seen in 25% of the preterm babies. Caesarean delivery, presence of one or more morbidities, mechanical ventilation, birth weight ≥ 1,500 g, and gestational age ≥ 32 weeks were identified as risk factors for THOP based on simple logistic regression. In multiple regression, mechanical ventilation and gestational age ≥ 32 weeks were significantly associated with THOP. CH was seen in 2 (3.1%) babies, and 1 of these cases had delayed TSH elevation.

Conclusion

Thyroid abnormalities are common in preterm admitted neonates. Mechanical ventilation is an independent risk factor for development of THOP.

Impact of maternal thyroid disease on neonatal thyroid status

OBJECTIVES

Prevalence of Maternal and congenital hypothyroidism is on the rise. To present the thyroid stimulating hormone screening results in babies born to hypothyroid mothers and assess the burden, aetiology of hypothyroidism in these babies.

METHODS

All antenatal mothers attending our hospital during the study period were enrolled into the study. Group I includes 249 term babies born to hypothyroid mothers and group II comprises 2154 newborns born to mothers who are euthyroid. Heel prick thyroid stimulating hormone was done for all newborns on day 3 for both groups. Confirmatory venous testing was done for all for babies in group I and screen positives belonging to group II. Evaluation and therapy done as per standard guidelines.

RESULTS

Thyroid stimulating hormone values in the two groups are presented. There was significant correlation between peak maternal thyroid stimulating hormone and neonatal day 3 heel prick in group I (r=0.7, P<0.05). The prevalence of positive screening test in groups I and II was 3.8 and 1.03% (p<0.05) whereas corresponding values for confirmed disease was 4.3 and 0.6%, respectively (p<0.05). Aetiological evaluation revealed both transient hypothyroidism (33.3%) and permanent hypothyroidism (66.6%).

CONCLUSION

4.3% of babies born to hypothyroid mothers develop congenital hypothyroidism; aetiology being both transient and permanent. A venous test by 3 weeks is helpful in these babies to improve case identification.

Diagnostic Value of Assessment of Serum Cortisol, Hepcidin and Thyroid Hormones Levels in Neonates with Late-Onset Sepsis

Neonatal sepsis is a clinical syndrome characterized by symptoms and signs of infection in the first twenty-eight days of life. Serum thyroid, cortisol and hepcidin are affected by neonatal sepsis. ; Aim of the Work: The aim of this study was to assess the diagnostic value of serum thyroid hormones including free triiodothyronine (free TT3) and free tetraiodothyronine (free TT4), serum cortisol and hepcidin levels through comparison of their concentrations between normal neonates and neonates with high probable late-onset sepsis. ; Patients and Methods: This case-control study was carried out on 40 neonates with suspected high probable late-onset neonatal sepsis based on clinical and laboratory finding who were admitted to NICU of Pediatric Department, Tanta University, Egypt in the period from April 2017 to May 2019 (group I) and 40 healthy neonates matched in age and sex as a control group (group II). For patients and controls, blood culture, highly sensitive C-reactive protein (H-s CRP), serum hepcidin, serum cortisol and thyroid hormones levels including free TT3 and free TT4 were assessed. ; Results: There were no significant differences between studied groups regarding weight, gestational age, sex and mode of delivery. H-s CRP, serum cortisol and hepcidin were significantly higher in group I than group II while serum-free TT3 and free TT4 were significantly lower in group I compared with controls (group II). There was significantly lower H-s CRP, serum hepcidin and cortisol and significantly higher serum-free TT3 and free TT4 in group I after antibiotic therapy compared to the same group before treatment while there were no significant differences between group I after antibiotic therapy and control group (group II) regarding the same parameters. There was a significant positive correlation between H-s CRP and serum hepcidin and cortisol in group I while there was a significant negative correlation between H-s CRP and free TT3 and free TT4. ROC curve of specificity and sensitivity of H-s CRP, serum hepcidin, cortisol, free TT3 and free TT4 in the prediction of neonatal sepsis shows that serum hepcidin had the highest sensitivity and specificity with 95% and 90% respectively followed by serum cortisol, H-s CRP, free TT3 and lastly free TT4. ; Conclusion and Recommendations: Neonates with high probable sepsis had significantly higher serum cortisol and hepcidin and significantly lower free TT3 and free TT4 compared with healthy neonates. These findings may draw our attention about the use of these markers in the diagnosis of neonatal sepsis which can help in early treatment and subsequently better prognosis.