Diagnosis of homozygosity and heterozygosity in congenital adrenal hyperplasia (CAH) and control of treatment.

In congenital adrenal hyperplasia the incidence of 21-hydroxylase deficiency is very high (approximately 1:7,000), whereas other enzyme defects such as 11-hydroxylase deficiency, 17-hydroxylase deficiency and 3 beta-hydroxysteroid dehydrogenase deficiency are much less frequent. The various forms of enzyme defects can be diagnosed by determining specific plasma steroids or specific urinary steroid metabolites. A new semi-automatic capillary gas liquid chromatography method has been introduced for the diagnosis of CAH and assessment of therapy. Heterozygous carriers of 21-hydroxylase deficiency can be detected in the general population by measuring 17-hydroxyprogesterone plasma levels after ACTH stimulation; however, results overlap with the general population. In families with a CAH index case, heterozygosity and homozygosity for the 21-hydroxylase deficiency gene can be detected by HLA-typing. 21-hydroxylase deficiency can be diagnosed prenatally by HLA-typing or by determining 17 OH-progesterone levels in the amniotic fluid.