Aldosterone, 11-desoxycorticosterone (DOC), and corticosterone (B).
Which laboratory tests exclude the diagnosis of Cushing’s syndrome?
Frequently, a simple overnight dexamethasone suppression test will assist in evaluating the patient with suspected Cushing’s syndrome. The patient is given 1 mg of dexamethasone at 11 P.M., and the plasma cortisol is measured at 8 a.m. the following morning. Values less than 5 j_ig/dl indicate normal suppression, values between 5 and 10 (ig/dl are borderline, and values 10 |xg/dl are abnormal.
An equally helpful test is a 24-hour urine measurement for free cortisol. Patients with elevated urinary free cortisol or nonsuppressible cortisol values should be evaluated for Cushing’s syndrome.
Which laboratory test is used to characterize Cushing’s disease?
A failure to suppress to 1-mg overnight dexamethasone (or its equivalent test, 0.5 mg of dexamethasone administered every 6 hours for 2 days) or an elevated 24-hour urine free cortisol is seen in patients with Cushing’s syndrome. Cushing’s disease (hypothalamic-pituitary Cushing’s) is distinguished from the other causes of Cushing’s syndrome by a 50% reduction in the plasma cortisol value after an 8-mg overnight dexamethasone suppression or a similar 50% suppression in urinary cortisol metabolites (17-hydroxycorticosteroids or free cortisol) with the long suppression test of 2 mg of dexamethasone every 6 hours for 2 days. Patients with pituitary Cushing’s disease have normal to slightly elevated plasma ACTH levels. They show enhanced responsiveness to corticotropin-releasing factor (CRF) testing, which helps distinguish them from patients with adrenal forms of Cushing’s syndrome and ectopic Cushing’s syndrome, where there is usually no ACTH response to CRF testing. Localization of pituitary Cushing’s disease is achieved by inferior petrosal sinus sampling for ACTH during a CRF infusion.
What clinical features in a hypertensive patient suggest the presence of pheochromocy-toma?
Headache, which is characteristically, but not always, pounding and severe
Palpitations with or without tachycardia
Excessive, inappropriate perspiration.