The only approved ACTH preparation (Cortrosyn®: Organon Pharmaceuticals, West Orange, NJ) has recently become available again, after a period of back-order. While other forms of ACTH may be available, their potency may not have been substantiated.

If a reliable source of ACTH is unavailable, basal cortisol concentrations can be used for assessing adrenal function. While this is not the ideal adrenal function test (because of possible wide daily fluctuations), it can be clinically useful when evaluated in conjunction with the patient's clinical signs and other laboratory findings.

Diagnostic screening test for hyperadrenocorticism:

• Basal cortisols are not useful.
• Consider urine cortisol:creatinine ratio (UCCR) and low-dose dexamethasone suppression (LDDS) test.

Diagnostic screening test for hypoadrenocorticism:

• Basal cortisol < 1 ug/dl is consistent with hypoadrenocorticism, if clinical signs are supportive.
• Basal cortisol > 5 ug/dl excludes a diagnosis of hypoadrenocorticism.
• Basal cortisol > 1 ug/dl and < 5 ug/dl is nondiagnostic.

Monitoring mitotane (Lysodren®) therapy for hyperadrenocorticism:

• If basal cortisol is < 1 ug/dl, consider stopping therapy and repeating the test in 2 to 4 weeks.
• If basal cortisol is > 1 ug/dl and < 5 ug/dl, and the patient is asymptomatic for hyperadrenocorticism, consider stopping the loading phase of mitotate therapy and starting maintenance therapy, or continuing with maintenance therapy at the same dosage of mitotane. Basal cortisol should be re-measured in 1 to 3 months.
• If basal cortisol is > 1 ug/dl and < 5 ug/dl, and the patient is symptomatic for hyperadrenocorticism, continue or start maintenance therapy and repeat the basal cortisol in 2 to 4 weeks.
• If the basal cortisol is > 5 ug/dl, consider continuing the loading phase of mitotane therapy for a longer period (usually 3 to 5 days), or raising the maintenance dosage by 25 to 50% and repeating the basal cortisol concentration immediately following the reloading period, or 1 month following maintenance therapy at the higher dosage.