Ovine CRH Stimulation and 8 mg Dexamethasone Suppression Tests in 323 Patients With ACTH-Dependent Cushing&apos;s Syndrome

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Abstract

Context

Determining the etiology of adrenocorticotropin (ACTH)-dependent Cushing's syndrome (CS) is often difficult. The gold standard test, inferior petrosal sinus sampling (IPSS), is expensive and not widely available.

Objective

Evaluate the performance of the corticotropin-releasing hormone stimulation test (CRH-ST) and the 8 mg high-dose dexamethasone suppression test (HDDST) in distinguishing Cushing's disease (CD) from ectopic ACTH syndrome (EAS).

Methods

Retrospective review in a tertiary referral center. A total of 323 patients with CD or EAS (n = 78) confirmed by pathology or biochemical cure (n = 15) in 96% underwent CRH-ST and HDDST performed between 1986 and 2019. We calculated test sensitivity (Se), specificity (Sp), positive predictive value (PPV), negative predictive value, and diagnostic accuracy (DA) for the diagnosis of CD, and determined optimal response criteria for each test, alone and in combination.

Results

The CRH-ST performed better than the HDDST (DA 91%, 95% CI 87-94% vs 75%, 95% CI 69-79%). Optimal response criteria were a ≥40% increase of ACTH and/or cortisol during the CRH test and a ≥69% suppression of cortisol during the HDDST. A ≥40% cortisol increase during the CRH test was the most specific measure, PPV 99%. Seventy-four percent of subjects had concordant positive CRH test and HDDST results, yielding Se 93%, Sp 98%, DA 95%, and PPV 99%, with a pretest likelihood of 85%. A proposed algorithm diagnosed 64% of patients with CD with near perfect accuracy (99%), obviating the need for IPSS.

Conclusion

CRH is a valuable tool to correctly diagnose the etiology of ACTH-dependent CS. Its current worldwide unavailability impedes optimal management of these patients.

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Most cited references 20

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Lynnette K Nieman, Beverly M K Biller, James Findling … (2015)

The objective is to formulate clinical practice guidelines for treating Cushing's syndrome.

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Pituitary magnetic resonance imaging in normal human volunteers: occult adenomas in the general population.

M Luciano, Michael Hall, J Doppman … (1994)

To determine the prevalence of focal lesions of the pituitary gland that suggest the presence of a pituitary adenoma in asymptomatic persons. 100 normal volunteers (70 women, 30 men; age range, 18 to 60 years old) were studied by high-resolution magnetic resonance imaging (MRI) of the pituitary gland before and after administration of gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA). Occult pituitary adenomas are identified at autopsy in 3% to 27% of unselected asymptomatic patients. The frequency of incidental pituitary adenomas detected by MRI in normal persons is unknown. The MRI scans from volunteers were randomly mixed with scans of 57 patients with Cushing disease and interpreted independently by three blinded reviewers. Seven women (10%) and three men (10%) had focal areas of decreased signal intensity in the pituitary gland after administration of Gd-DTPA. The lesions ranged from 3 to 6 mm in greatest diameter and were diagnosed as pituitary adenomas by at least two of the three reviewers. When similar lesions were detected on MRI scans in patients with Cushing disease, the positive predictive value for identification of an adenoma at that site was 86%. About 10% of the normal adult population have pituitary abnormalities on MRI scans that are compatible with the diagnosis of asymptomatic pituitary adenomas. Most pituitary adenomas remain asymptomatic and do not require treatment.

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Cushing's syndrome due to ectopic corticotropin secretion: twenty years' experience at the National Institutes of Health.

R Wesley, Karel Pacak, David J Torpy … (2005)

Ectopic ACTH secretion (EAS) is difficult to diagnose and treat. We present our experience with EAS from 1983 to 2004. The study was performed at a tertiary care clinical research center. Ninety patients, aged 8-72 yr, including 48 females were included in the study. Tests included 8 mg dexamethasone suppression, CRH stimulation, inferior petrosal sinus sampling (IPSS), computed tomography, octreotide scan, magnetic resonance imaging, and/or venous sampling. Therapies, pathological examinations, and survival were noted. Eighty-six to 94% of patients did not respond to CRH or dexamethasone suppression, whereas 66 of 67 had negative IPSS. To control hypercortisolism, 62 patients received medical treatment, and 33 had bilateral adrenalectomy. Imaging localized tumors in 67 of 90 patients. Surgery confirmed an ACTH-secreting tumor in 59 of 66 patients and cured 65%. Nonthymic carcinoids took longest to localize. Deaths included three of 35 with pulmonary carcinoid, two of five with thymic carcinoid, four of six with gastrinoma, two of 13 with neuroendocrine tumor, two of two with medullary thyroid cancer, one of five with pheochromocytoma, three of three with small-cell lung cancer, and two of 17 with occult tumor. Patients with other carcinoids and ethesioneuroblastoma are alive. IPSS best identifies EAS. Initial failed localization is common and suggests pulmonary carcinoid. Although only 47% achieved cure, survival is good except in patients with small-cell lung cancer, medullary thyroid cancer, and gastrinoma.