[Risk factors for neonatal congenital hypothyroidism: a Meta analysis]

[Investigation of influencing factors and reference ranges for thyroid function in hospitalized preterm infants at the age of 7 days]

OBJECTIVES

To investigate the influencing factors and reference ranges for thyroid function in preterm infants at the age of 7 days, with the aim of avoiding unnecessary clinical reexamination and intervention.

METHODS

A retrospective analysis was performed for the data of 685 preterm infants from January 2020 to January 2023. According to gestational age and birth weight, they were divided into a high-risk group (gestational age <34 weeks or birth weight<2 000 g; 228 infants) and a low-risk group (gestational age ≥34 weeks and birth weight ≥2 000 g;457 infants). The influencing factors for thyroid function were analyzed, and 95% reference range was calculated.

RESULTS

Gestational age, birth weight, birth season, sex, and assisted reproduction were the influencing factors for thyroid function (P<0.05). For the preterm infants in the high-risk group, the reference ranges of free triiodothyronine (FT3), free thyroxine (FT4), total triiodothyronine (TT3), total thyroxine (TT4), and thyroid stimulating hormone (TSH) were 2.79-5.40 pmol/L, 8.80-25.64 pmol/L, 0.80-2.15 nmol/L, 50.06-165.09 nmol/L, and 0.80-18.57 μIU/mL, respectively. For those in the low-risk group, the reference ranges of these indicators were 3.08-5.93 pmol/L, 11.17-26.24 pmol/L, 1.02-2.27 nmol/L, 62.90-168.95 nmol/L, and 0.69-13.70 μIU/mL, respectively. FT3, FT4, TT3, and TT4 were positively correlated with gestational age (P<0.05); FT3, FT4, TT3, and TT4 were positively correlated with birth weight (P<0.05); TSH was negatively correlated with birth weight (P<0.05).

CONCLUSIONS

Thyroid function in preterm infants at the age of 7 days is affected by the factors such as gestational age and birth weight, and the reference ranges of thyroid function in preterm infants at the age of 7 days should be established based on gestational age and birth weight.

Increased incidence of congenital hypothyroidism in China: An analysis of 119 million screened newborns

Despite the lack of nationwide epidemiological studies, congenital hypothyroidism (CH) incidence in China has increased. We aimed to evaluate the trends of CH and the possible reasons behind them. Data from screened newborns from the Chinese Newborn Screening Information System from 2012 to 2019 was collected. We applied the Bayesian hierarchical Poisson regression model and meta-analysis to estimate incidence or proportion over the years. The estimated CH incidence increased from 4.01 per 10,000 births in 2012 to 5.77 per 10,000 births in 2019. The average annual growth rate (ARG) of CH incidence for all provinces varied from 0.59 to 20.96%. The most rapid rise in incidence was observed in cases with an initial thyroid stimulating hormone (TSH) concentration of < 10 mIU/L. The meta-analysis results showed that the proportion of permanent CH increased by 0.024% (95%CI: 0.011%, 0.037%) annually. Each 1 mIU/L decrease in TSH cutoff value was associated with a 2.96% increase in CH incidence. In the same period, the proportion of premature CH cases increased from 6.60 to 9.10%, which was much higher than the increase in preterm births. A significant relationship was not found between provincial growth rates in screening coverage and provincial baseline incidences of CH.  Conclusion: CH incidence has substantially increased in China. The slight adjustment of the TSH cutoff value and increasing preterm birth rate contribute to such a trend; however, the contribution is limited. What is Known: • An uptrend in congenital hypothyroidism (CH) incidence has been reported in many European and American countries in the last two decades; however, no studies have been conducted in China to explain the increased CH incidence. • We provide a detailed epidemiological report on the trends of CH during 2012-2019 in China, with an attempt to explore the reasons behind it. What is New: • This first-ever national-wide epidemiological report in China showed an uptrend in CH incidence with variations over regions and CH subtypes. The mild lowering of TSH cutoff values and the increasing preterm birth rate contributed to this uptrend.

Analysis of Risk Factors and Screening Results of Neonatal Congenital Hypothyroidism in a Tertiary Care Center of Southern China

Objective

To explore the risk factors for neonatal congenital hypothyroidism (CH) and the influencing factors of false-positive results in CH screening.

Methods

In this study, 255 neonatal patients with CH who completed the screening and further diagnosis and 366 neonates with positive CH screening results and normal thyroid function were selected as the case group. 246 healthy neonates with normal thyroid function were selected as the control group. Gestational age, birth-weight, maternal age, small for gestational age (SGA), perinatal factors (gestational thyroid dysfunction, gestational diabetes mellitus, etc.) were used as influencing factors, using χ ² tests were performed for comparison. The statistically significant variables were analyzed with Logistic multiple regression models, and the difference was considered statistically significant (P<0.05).

Results

There were statistical differences in the SGA, maternal gestational diabetes mellitus, thyroid disease, and the proportion using assisted reproduction technology among the case group, false-positive screening group, and control group (χ ² was 11.943, 6.857, 6.999, 9.732, respectively, P < 0.05). The results of multivariate logistic regression analysis showed that the gestational thyroid disease (OR = 8.452, 95% CI:1.051-67.982), gestational diabetes mellitus (OR = 2.654, 95% CI:1.051-6.706), and assisted reproduction (OR = 0.194, 95% CI:0.041-0.911) were the influencing factors for neonatal CH, and the difference was statistically significant (P < 0.05). The SGA (OR = 2.556, 95% CI:1.027-6.361), gestational thyroid disease (OR = 7.801, 95% CI:1.03-59.057), gestational diabetes mellitus (OR = 2.731, 95% CI:1.18-6.322), and assisted reproduction (OR = 0.28, 95% CI:0.102-0.765) were the influencing factors of the false-positive screening results of neonatal CH. The difference was statistically significant (P < 0.05).

Conclusion

Neonatal CH and positive screening results are influenced by assisted reproduction, gestational thyroid dysfunction, gestational diabetes mellitus, and SGA.

Incidence of congenital hypothyroidism by gestational age: a retrospective observational study

BACKGRUOUND

Congenital hypothyroidism (CH) is the leading cause of preventable physical and intellectual disabilities. This study aimed to assess the incidence and clinical characteristics of CH in newborns.

METHODS

We retrospectively reviewed the medical records of all newborns delivered at the Pusan National University Hospital between January 2011 and March 2021. The incidence of CH was compared according to gestational age, birth weight, and small for gestational age (SGA). The patients aged ≥3 years who could not maintain normal thyroid function and required levothyroxine treatment were diagnosed with permanent CH. Logistic regression analysis was performed to compare CH risks.

RESULTS

Of 3,722 newborns, 40 were diagnosed with CH (1.07%). Gestational age and birth weight were significantly associated with CH incidence. The odds ratios (ORs) of CH in infants delivered at 32-37, 28-31, and <28 weeks were 2.568 (95% confidence interval [CI], 1.141-5.778), 5.917 (95% CI, 2.264-15.464), and 7.441 (95% CI, 2.617-21.159) times higher, respectively, than those delivered at term. The ORs of CH in infants weighing 1,500-2,499 g, 1,000-1,499 g, and <1,000 g were 4.664 (95% CI, 1.928-11.279), 11.076 (95% CI, 4.089-29.999), and 12.544 (95% CI, 4.350-36.176) times greater, respectively, than those in infants weighing ≥2,500 g. The OR of CH was 6.795 (95% CI, 3.553-13.692) times greater in SGA than in non-SGA infants.

CONCLUSION

The CH incidence in South Korea has increased significantly compared with that in the past. Gestational age, birth weight, and SGA were significantly associated with CH incidence.

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.