Screening for neonatal endocrinopathies: rationale, methods and results.

The measurement of thyrotropin or thyroxine from dried blood spots collected from neonates allows diagnosis before clinical manifestations develop, and prevents mental deficiency from congenital hypothyroidism. However, severely hypothyroid newborns remain at risk of cognitive problems that may be avoided if they are treated within two weeks of birth, hence the importance of a quick turnaround time of the screening programme. This also applies to screening for congenital adrenal hyperplasia due to 21-hydroxylase deficiency based on the measurement of 17-hydroxy-progesterone from dried blood; this was primarily designed to prevent neonatal deaths from acute adrenal insufficiency. This goal can be achieved by a high degree of clinical awareness of the diagnosis, but this has only been reported in a few jurisdictions. Furthermore, biochemical screening allows earlier treatment. On the other hand, there are many false positives, mostly in premature infants, so screening for 21-hydroxylase deficiency has not been universally adopted.