Journal of endocrinological investigation
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The posterior pituitary hormone vasopressin is one of the principal endocrine regulators of fluid and electrolyte balance. Tests of posterior pituitary function are based on the physiology and pathophysiology of vasopressin, and involve studies that aim at defining the production and action of the hormone in response to fixed stimuli with reference to standard normal ranges.
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The diagnosis of adrenal hypofunction is suggested by clinical features and confirmed by biochemical testing. The characteristic features of acute primary adrenal insufficiency include orthostatic hypotension, fever, and hypoglycemia. By contrast, patients with chronic primary adrenal insufficiency have a longer history of malaise, as well as fatigue, anorexia, diarrhea, weight loss, joint and back pain, and darkening of the skin. ⋯ The 250 microg ACTH test works well to identify primary adrenal hypofunction, but can only detect secondary adrenal hypofunction when there is sufficient time for the glands to atrophy because of reduced endogenous ACTH stimulation. The 1 microg ACTH test has been advocated in the setting of possible secondary adrenal insufficiency, but its widespread use has been mitigated by the lack of a commercial preparation of this small dose and controversy regarding diagnostic criteria. Ultimately, the choice of test should be individualized for each patient, with knowledge of the available reference assays and the vagaries of each test.