The adrenal gland produces hormones that affects growth, development and stress, and also helps to regulate kidney function. There are two parts of the adrenal glands, the adrenal cortex and the adrenal medulla. The adrenal cortex produces mineralocorticoids , which regulate salt and water balance within the body, glucocorticoids (including cortisol ) which have a wide number of roles within the body, and androgens , hormones with testosterone-like function.  The adrenal medulla produces epinephrine (adrenaline) and norepinephrine (noradrenaline).  Disorders of the adrenal gland may affect the production of one or more of these hormones.
Patients can eat and drink normally and take all their usual medications prior to the test. Estrogen containing medications, including the contraceptive pill and hormone replacement therapy, should be stopped for six weeks prior to measuring serum cortisol. This is because estrogen induces cortisol binding globulin and leads to elevations in measured serum cortisol. Any steroid containing medications should also be documented, and avoided if possible, as they may interfere with the hypothalamo-pituitary-adrenal axis, or cross react with the cortisol assay.
During minor illness (., flu or fever >38° C [° F]) the hydrocortisone dose should be doubled for 2 or 3 days. The inability to ingest hydrocortisone tablets warrants parenteral administration. Most patients can be educated to self administer hydrocortisone, 100 mg IM, and reduce the risk of an emergency room visit. Hydrocortisone, 75 mg/day, provides adequate glucocorticoid coverage for outpatient surgery. Parenteral hydrocortisone, 150 to 200 mg/day (in three or four divided doses), is needed for major surgery, with a rapid taper to normal replacement during the recovery. Patients taking more than 100 mg hydrocortisone/day do not need any additional mineralocorticoid replacement. All patients should wear some form of identification indicating their adrenal insufficiency status.