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Thyroid function profiles in small versus appropriate for gestational age stable neonates with implications for
Monisha Rameshbabu1, Shiba Subramanian2, Giridhar Sethuraman1
1Department of Neonatology, Chettinad Hospital and Research Institute, Chettinad Academy of Research and Education, Kelambakkam, Tamil Nadu, India.
Insights
Small-for-gestational-age (SGA) neonates show higher thyroid-stimulating hormone (TSH) levels than appropriate-for-gestational-age (AGA) neonates. Tailoring TSH screening cutoffs for SGA infants may improve congenital hypothyroidism detection and reduce unnecessary recalls.
Area of Science:
- Neonatal endocrinology
- Pediatric screening protocols
- Growth and development studies
Background:
- Thyroid hormones are crucial for neonatal development.
- Small-for-gestational-age (SGA) neonates face increased risks of thyroid dysfunction.
- Current screening practices may not optimally identify thyroid issues in SGA infants.
Purpose of the Study:
- To compare thyroid-stimulating hormone (TSH) and free thyroxine (FT4) levels in SGA versus appropriate-for-gestational-age (AGA) neonates.
- To evaluate the implications for neonatal hypothyroidism screening protocols.
- To investigate factors influencing TSH and FT4 levels in neonates.
Main Methods:
- Retrospective cross-sectional study of 756 neonates (268 SGA, 488 AGA) in Southern India.
- Analysis of serum TSH and FT4 levels measured at 48-72 hours of life.
- SGA defined by birth weight below the 10th percentile using Fenton's growth charts.
Main Results:
- SGA neonates exhibited significantly higher TSH levels (median 5.33 mIU/L) compared to AGA neonates (median 4.09 mIU/L).
- Elevated TSH (>10 mIU/L) requiring recall was more frequent in SGA infants (18% vs. 8%).
- FT4 levels were comparable between SGA and AGA groups; SGA status, low birth weight, and cesarean delivery predicted higher TSH.
Conclusions:
- SGA neonates demonstrate elevated TSH levels at 48-72 hours, indicating potential thyroid dysfunction risk.
- Comparable FT4 levels suggest TSH is a more sensitive marker for thyroid changes in SGA infants.
- Developing tailored TSH screening cutoffs for SGA neonates could enhance screening efficiency and reduce unnecessary interventions.
Objective:
Thyroid hormones are critical for neonatal growth and development, with small-for-gestational-age (SGA) neonates at greater risk of thyroid dysfunction. This study aimed to compare thyroid-stimulating hormone (TSH) and free thyroxine (FT4) levels between small-for-gestational-age (SGA) and appropriate-for-gestational-age (AGA) neonates, potentially guiding screening practices.
Methods:
A retrospective cross-sectional study was conducted at a tertiary care center in Southern India, including stable term and late preterm neonates born consecutively from Jan to Sep 2024. Medical records were retrieved and relevant clinical data was collected. Routine neonatal hypothyroidism screening at 48-72 h of life measured serum TSH and FT4 levels via venous samples. SGA was defined as birth weight below the 10th percentile using Fenton's growth charts.
Results:
Among 756 neonates, 268 were SGA and 488 were AGA. Median [IQR] gestational age was 38 weeks [37-39] and birth weight was 2,800 g [2,500-3,009]. SGA neonates had significantly higher median [IQR] TSH levels (mIU/L) compared to AGA neonates [5.33 [2.8-8.7] vs. 4.09 [2.3-6.6], MD 1.24 (95% CI = 0.38, 2.09.) p < 0.01]. Elevated TSH (>10 mIU/L) requiring recall was more frequent in SGA than AGA neonates (18% vs. 8%, p < 0.01). A weak negative but significant correlation was observed between birth weight and TSH (rho = -0.12, p < 0.01). Median [IQR] FT4 levels (ng/dl) were comparable between SGA and AGA groups [2.02 [1.69-2.41] vs. 2.02 [1.65-2.40]; p = 0.69]. Multivariate regression analysis revealed SGA status, LBW and cesarean delivery as independent predictors of TSH levels, while prematurity and the need for resuscitation were independent predictors of FT4 levels.
Conclusion:
SGA neonates exhibit significantly higher serum TSH levels at 48-72 h compared to AGA neonates. FT4 levels were comparable between the groups. Tailored TSH cutoffs for SGA neonates could reduce unnecessary recalls and resampling during congenital hypothyroidism screening.
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