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Serum alpha-fetoprotein--a biochemical indicator of prenatal hypothyroidism
Insights
Serum alpha-fetoprotein (AFP) levels are higher in infants with true congenital hypothyroidism. This finding suggests AFP analysis can identify infants at risk for developmental issues.
Area of Science:
- Biochemistry
- Pediatrics
- Endocrinology
Background:
- Congenital hypothyroidism (CH) screening relies onThyroid-Stimulating Hormone (TSH) tests.
- Elevated serum alpha-fetoprotein (AFP) has been observed in infants with CH.
- The clinical significance of elevated AFP in CH screening requires further elucidation.
Purpose of the Study:
- To investigate serum AFP levels in infants with positive TSH screening tests for CH.
- To determine if AFP levels can differentiate true from false positive CH screening results.
- To explore the relationship between AFP levels, CH, and skeletal maturation.
Main Methods:
- Serum AFP levels were measured in infants aged 10-30 days with positive TSH screening tests.
- Comparison of AFP levels between infants with true CH and false positive screening results.
- Correlation analysis between AFP levels and roentgenological skeletal maturation index.
Main Results:
- Serum AFP levels were significantly higher in infants with true CH compared to false positives.
- 27 out of 43 infants with confirmed CH exhibited elevated serum AFP.
- Postnatal AFP elimination rates were similar in hypothyroid and euthyroid infants, suggesting increased synthesis in CH.
- Serum AFP levels showed an inverse correlation with skeletal maturation.
Conclusions:
- Elevated serum AFP in infants with positive TSH screening may indicate prenatal hypothyroidism.
- Serum AFP analysis is a valuable tool for identifying infants with CH at risk of neuropsychological sequelae.
- Increased AFP synthesis, not altered elimination, likely accounts for higher levels in CH infants.
Abstract:
Serum alpha-fetoprotein (AFP) was analysed at 10-30 days of age in infants with positive TSH screening tests for congenital hypothyroidism. These levels were significantly higher in infants with true positive screening tests than in those with false positive tests; 27 of 43 infants with congenital hypothyroidism had serum AFP levels above the age-related reference range. The postnatal rate of elimination of AFP from serum did not differ in hypothyroid and euthyroid infants, indicating that the difference in serum AFP was due to more extensive synthesis in hypothyroid individuals. The level of serum AFP was inversely correlated with the roentgenological skeletal maturation index. It is postulated that increased serum AFP is caused by prenatal hypothyroidism and that analysis of serum AFP is a valuable tool to identify those infants with congenital hypothyroidism who are at risk of neuropsychological sequelae.