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Neonatal thyroid function in congenital hypothyroidism
Insights
Congenital hypothyroidism in infants is challenging to diagnose early due to normal triiodothyronine (T3) levels initially. However, T3 levels normalize over time, correlating with disease severity, supporting newborn screening programs.
Area of Science:
- Pediatric Endocrinology
- Neonatal Screening
- Thyroid Disorders
Background:
- Congenital hypothyroidism (CH) is a common endocrine disorder in newborns.
- Early diagnosis and treatment are crucial to prevent intellectual disability and developmental delays.
- Newborn screening programs are vital for identifying CH promptly.
Purpose of the Study:
- To investigate the initial thyroid hormone profiles in infants with CH detected via newborn screening.
- To explore the relationship between triiodothyronine (T3) levels, thyrotropin (TSH) levels, and clinical features of CH.
- To understand the diagnostic challenges and the rationale for early treatment in CH.
Main Methods:
- Analysis of cord blood samples from seven infants diagnosed with CH through newborn screening.
- Measurement of thyroxine (T4), triiodothyronine (T3), and thyrotropin (TSH) levels.
- Follow-up assessment of T3 levels and correlation with TSH and clinical manifestations.
Main Results:
- Initial T4 levels were low, TSH levels were elevated, and T3 levels were normal in infants with CH.
- In five out of seven infants, T3 levels normalized upon follow-up.
- A significant negative correlation was observed between T3 levels and CH severity (indicated by TSH and clinical features).
Conclusions:
- Normal initial T3 levels in CH can complicate early diagnosis.
- The normalization of T3 levels over time may explain diagnostic difficulties in the first few months of life.
- These findings reinforce the importance of newborn screening programs for congenital hypothyroidism and highlight the effectiveness of early treatment.
Abstract:
In the cord blood of seven infants with congenital hypothyroidism detected in our newborn screening programs, thyroxine values ranged from 2.5 to 6.7 mug/dl and thyrotropin, from 105 to 975 muU/ml; triiodothyronine values were normal. On follow-up, T3 levels increased to normal in five infants, there was a significant negative correlation between the T3 value and the severity of thyroprevia as reflected in the TSH levels and the number of clinical features present. This increase in T3 may explain in part why the diagnosis of this disease is difficult during the first few months of life and why early treatment is effective. This observation provides further rationale for the widespread institution of newborn screening programs for congenital hypothyroidism.