The purpose of this study is to determine if dexamethasone given at night is a more effective treatment for congenital adrenal hyperplasia in young children than standard three times per day hydrocortisone. Our hypothesis is that nocturnal dexamethasone will lead to more efficient suppression of the hypothalamic-pituitary-adrenal axis. We performed a cross-over trial comparing hormonal control during two 24-hour hospitalizations, one on hydrocortisone and one on nocturnal dexamethasone.

This is a Phase II clinical trial, intended to estimate the effect of instituting Dexamethasone therapy in comparison to prior standard therapy. Each subject provides his own baseline data. There is no control group. Patients with CAH who meet inclusion criteria will be admitted to the clinical research center for two 24 hour hospitalizations. Adrenal hormone profiles will be measured during each hospitalization. The patient will take his or her baseline hydrocortisone regimen during one hospitalization and a new regimen consisting of a single daily nocturnal dose of Dexamethasone during the second hospitalization.

Inclusion Criteria:

• Classic salt-wasting 21-hydroxylase deficient congenital adrenal hyperplasia
• Pre-pubertal children with bone ages below 8 years

Exclusion Criteria:

• Age less than 2 years
• Patients with additional medical conditions necessitating glucocorticoid therapy.
• Patients on phenytoin, barbiturates, and rifampin as these medications accelerate the metabolism of glucocorticoids.
• Patients on ketoconazole as this medication increases the bioavailability of glucocorticoids.