It was British researchers who discovered the effectiveness of dexamethasone, a cheap drug, in treating covid-19 patients who are admitted to hospital.
Unlike pituitary adenomas, ectopic sites of ACTH productions typically don't respond even to high doses of dexamethasone, and the serum cortisol remains high.
Another option is also the dexamethasone suppression test, which is when a person is given a low dose of dexamethasone, which is an exogenous steroid that suppresses ACTH production in the pituitary gland.
By logging on to the hospital system I'd been able to follow the course of his admission: he'd been started on the steroid dexamethasone, and a new antiviral drug, and was making a good recovery.