The aim of this study is to compare the effects of tablet treatment, circadian and combined circadian and ultradian subcutaneous hydrocortisone infusion on steroid metabolism and tissue responses to therapy.

The conventional glucocorticoid replacement therapy in primary adrenal insufficiency (Addison's disease) and congenital adrenal hyperplasia renders the cortisol levels unphysiological, which may cause symptoms and long-term complications. This therapeutical approach does not enable to restore physiological circadian and ultradian rhythm of glucocorticoids. Current studies conclude that constant or unphysiological administration of glucocorticoids leads to abnormal gene transcription and causes sides effect of glucocorticoids treatment and long standing complications Glucocorticoid replacement is technically feasible by continuous subcutaneous hydrocortisone infusion, which can mimic not only the normal diurnal cortisol rhythm, but potentially also the ultradian cadence.

This is a pilot trial with an open cross-over design of 3 x minimum 2 weeks in 10 patients comparing the effects of tablet treatment versus continuous subcutaneous hydrocortisone infusion versus ultradian subcutaneous hydrocortisone infusion on serum, salivary, tissue hormonal response and glucocorticoid related gene expression.

Inclusion Criteria:

1. clinical diagnosis of primary adrenal insufficiency
2. Written informed consent

Exclusion Criteria:.

1. Diabetes mellitus
2. Severe cardiovascular disease
3. Active malignant disease
4. Pregnancy or breast feeding
5. treatment with interfering drugs
6. Intake of grapefruit juice