Congenital Adrenal Hyperplasia Once Daily Hydrocortisone Treatment

Inclusion Criteria: * males and females aged \>18 years; * established diagnosis of adrenal insufficiency in congenital adrenal hyperplasia due to 21-hydroxylase deficiency; * stably treated with conventional glucocorticoids, available to change their regimen according to random allocation * written informed consent/assent to participate in the study in compliance with local regulations. Exclusion Criteria: * clinical or laboratory signs of severe cerebral, respiratory, hepatobiliary or pancreatic diseases, renal dysfunction, gastrointestinal emptying, or motility disturbances (i.e. chronic diarrhea), significant psychiatric illnesses; * history of/or current alcohol and/or drug abuse; * night shift workers; * underlying diseases that could necessitate treatment with glucocorticoids; * therapies with hepatic enzyme induction drugs interfering with glucocorticoid kinetics, or immunosuppressive steroid therapy; * patients with a documented intolerance/known hypersensitivity to dual release hydrocortisone; * vulnerable populations, such as elderly, cancer patients, pregnant and lactating women; * history of non-compliance to medical regimens, or potentially unreliable patients