PubMed · 9172545
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K Tanaka, M Toriumi, S Itoh, Y Ogino. 1997. [Metyrapone test].. https://pubmed.ncbi.nlm.nih.gov/9172545/
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The present case report describes the rare clinical presentation of diabetes insipidus in a patient with an ectopic ACTH syndrome (morning plasma cortisol 1.10 mumol/l, morning plasma ACTH 322 ng/l) due to disseminated small cell lung cancer including a metastasis in the posterior pituitary. The patient was treated by combination chemotherapy and at the same time received octreotide to control hypercortisolism and desmopressin (DDAVP) to control polyuria. Partial tumour remission was achieved resulting in decreased cortisol production and disappearance of the diabetes insipidus. Medical treatment could be discontinued. Several months later tumour regrowth occurred, with recurrence of hypercortisolism (mean morning plasma cortisol 0.74 mumol/l, mean morning plasma ACTH 112 ng/l) but without diabetes insipidus. Early treatment of hypercortisolism in patients with an ectopic ACTH syndrome and disseminated small cell lung cancer may prolong survival and improve the quality of life.
OBJECTIVE: The high-dose dexamethasone (dex) suppression test of cortisol secretion (8 x 2 mg dex over two days or 8 mg overnight) is a mainstay in the differential diagnosis of Cushing's syndrome (CS). In some patients with pituitary Cushing's disease (CD), however, plasma cortisol is not suppressed to < 50% of control by 8 mg of dex. We therefore hypothesized that a higher dose of dex might produce more effective suppression of cortisol secretion in CD. DESIGN AND SUBJECTS: We routinely tested the diagnostic efficacy of a very high dose of dex (32 mg, i.e. 4 x 8 mg in 24 hours) in comparison with the 8 mg overnight dex test in a population of patients with CD, in which an unusually high percentage was refractory to 8 mg dex. End points were the suppression of plasma cortisol, plasma ACTH and urinary free cortisol (UFC) to < 50% of control. Corticotrophin releasing hormone (human CRH) tests were also performed. RESULTS: Eleven out of 26 (11/26) patients with CD (42%), among them six with pituitary macro-adenomas, failed to show suppression of plasma cortisol after 8 mg dex. Five out of 19 patients (26%) with CD failed to suppress after 32 mg dex. Only 3/19 (16%) failed to suppress UFC after 32 mg dex. In nonpituitary CS (n = 11), only one patient with macro-nodular adrenal hyperplasia showed significant suppression of plasma cortisol, but not UFC, after 32 mg dex. ACTH suppression after 8 or 32 mg dex was often less pronounced than that of cortisol and was of no diagnostic value. Cortisol stimulation by > or = 23% after hCRH injection differentiated 100% of patients with CD from other forms of CS. CONCLUSION: In this series, the hCRH test was the most reliable test for the differential diagnosis of Cushing's syndrome. The 32 mg dexamethasone test with measurement of urinary free cortisol was clearly superior to the 8 mg test and to other aspects of the very high dose dexamethasone test. It can be recommended for 'non-suppressible' patients with ACTH-dependent Cushing's syndrome and can be performed on outpatients.