The corticotrophin-releasing hormone test is the most reliable noninvasive method to differentiate pituitary from ectopic ACTH secretion in Cushing's syndrome

OBJECTIVE

It has been reported previously that the paired interpretation of the corticotrophin-releasing hormone (CRH) test and the 8-mg dexamethasone suppression test (HDDST) could have higher diagnostic power than any single test in the differential diagnosis of ACTH-dependent Cushing's syndrome. This finding has not been confirmed thereafter in large series. The aim of the present study has been to assess the operating characteristics of either the CRH test or the overnight HDDST and also to evaluate the potential utility of combining the interpretation of both tests in the differential diagnosis of ACTH-dependent Cushing's syndrome.

DESIGN AND PATIENTS

We have reviewed the medical records of 59 consecutive cases with ACTH-dependent Cushing's syndrome: 49 patients with proven Cushing's disease (CD) and 10 patients with proven ectopic ACTH syndrome (EAS). Univariate curves of the receiver operating characteristics (ROC) have been performed to define the best cut-off values, the sensitivity and the specificity for CRH and overnight HDDST. A comparison between the areas under the ROC curves has also been performed.

RESULTS

For the CRH test, the point on the ROC curve closest to 1 corresponded to a value of ACTH percentage increment of 50%[sensitivity 86% (72.6-94.8) and specificity 90% (55.5-98.3)]. The best threshold for cortisol percentage (30%) increment gave inferior results [sensitivity 61% (45.5-75.6) and specificity 70% (34.8-93.0)]. For the HDDST, the point on the ROC curve closest to 1 corresponded to a value of cortisol decrease from the baseline of 50%[sensitivity 77% (62.7-88.5), specificity 60% (26.4-87.6)]. The area under the ROC curve of the ACTH percentage increment after CRH was significantly greater than the area under the diagonal [0.9 (0.7-1.0), P= 0.0001]. Conversely, the area under the cortisol percentage decrement after dexamethasone was not different from that obtained by chance [0.7 (0.5-0.9), P= ns]. The area under the ROC curve of CRH is significantly greater than that of overnight HDDST (P = 0.03). A correct diagnosis has been achieved by the CRH test in 86.5% of cases and by the HDDST in 73% (P = 0.06). The combination of both tests has given a correct diagnosis in a significantly lower percentage of cases than the CRH test alone (69%, P= 0.04). The bilateral inferior petrosal sinus sampling (BIPSS) has been performed in 29 patients (24 CD, five EAS) who had negative imaging and/or discordant results of the noninvasive tests. Considering the criterion of a central to peripheral ACTH ratio > 3 after CRH stimulation, a correct diagnosis was achieved in all cases.

CONCLUSIONS

The present data suggest that the CRH is likely to be the most reliable noninvasive diagnostic procedure for the differential diagnosis of the ACTH-dependent Cushing's syndrome. The criterion for a diagnosis of EAS is an ACTH percentage increment lower than 50%. The use of a combination of tests is not recommended because it does not add valuable information and may even impair the outcome of the CRH test. Cases with discordant results in pituitary imaging and CRH test should undergo BIPSS. The validity of this approach, which is straightforward and easily applicable in clinical practice, should be verified in larger series.

Characterisation of ACTH related peptides in ectopic Cushing's syndrome

Adrenocorticotrophin (ACTH) is derived by cleavage from the precursor, pro-opiomelanocortin (POMC), and depending on the degree of processing by the tissue or tumor, there is the potential for a number of ACTH-related peptides to be secreted from POMC expressing cells. Previous chromatographic approaches have indicated the presence of high molecular weight forms of ACTH in the human peripheral circulation. However a quantitative assessment of the degree of processing requires two-site immunoradiometric assays which distinguish ACTH precursors and ACTH. Using this approach, we have previously identified the precursors of ACTH (POMC and proACTH) in the circulation of normal subjects in the range 5-40 pmol/l, which suggests that processing in the normal pituitary cell is incomplete. This study aimed to examine the extent of POMC processing by tumors that give rise to Cushing's Syndrome as a means of evaluating its usefulness as a diagnostic marker. In a retrospective analysis of 86 patients with Cushing's Syndrome, 34/35 patients with pituitary tumors had low levels of ACTH precursors (below 100 pmol/l) and the mean ratio of ACTH precursors:ACTH was 5:1 which indicates that these tumors do process POMC to ACTH relatively efficiently. In ectopic Cushing's Syndrome, it is unlikely that the extra-pituitary tumor cells, process POMC as efficiently. Therefore increased prevalence of ACTH precursors in the circulation would be expected and this was substantiated by the large excess of ACTH precursors (139-18,000 pmol/l) in the circulation of the 51 patients with the ectopic ACTH Syndrome. The diagnostic accuracy of the measurement of ACTH precursors was then prospectively compared with a group of 62 patients undergoing the current "gold standard" test of inferior petrosal sinus sampling (IPSS). All those patients with ACTH precursors below a diagnostic cut-off of 100 pmol/l were subsequently shown to have pituitary tumors, whereas levels of >100 pmol/l were seen in the four patients with ectopic tumors. In comparison the IPSS had a specificity of 100% but a sensitivity of 93% and for these false negative results the ACTH precursors proved diagnostically useful. Therefore measurement of ACTH precursors offers a simple non-invasive diagnostic test for the differential diagnosis of Cushing's Syndrome which compares favourably with IPSS.

The limited value of the desmopressin test in the diagnostic approach to Cushing's syndrome

OBJECTIVE

The desmopressin test is generally regarded as an alternative to the CRH test but it is unclear whether desmopressin is as effective as CRH in the differential diagnosis of ACTH-dependent Cushing's syndrome. However, a precise assessment of the operating characteristics of the desmopressin test in comparison with the CRH test has not been reported. The aim of the present study was to make a comparative evaluation of desmopressin and CRH tests in a consecutive cohort of patients with ACTH-dependent Cushing's syndrome and in a group of healthy subjects.

DESIGN AND SUBJECTS

We studied 34 patients with Cushing's disease (CD) and nine patients with ectopic ACTH syndrome (EAS). The control group included 30 healthy subjects. Estimates of sensitivity and specificity were determined for a value of ACTH percent increment (Delta%) > 35% and for a Delta % > 50%, following either desmopressin or CRH, to differentiate CD from EAS. The sensitivity and specificity of a composite rule requiring an ACTH net increment (Delta) > 4.5 pmol/l at both values of Delta % was also calculated. When evaluating cortisol responses, the criteria were Delta % > 20% and Delta > 193 nmol/l. Moreover, to allow comparison of individual end points of the desmopressin and CRH tests at multiple levels of Delta % or Delta either for ACTH or cortisol without the bias of predetermined criteria, univariate curves of the receiver operating characteristics (ROC) were constructed by plotting the sensitivity against 1 - specificity at each level.

RESULTS

In the patients with CD, the frequency of ACTH response was of 90% after both tests while the figures for cortisol were 73% after CRH and 77% after desmopressin, respectively. In the 15 patients who underwent both tests the magnitude of ACTH and cortisol responses induced by the 2 stimuli were fully comparable. In the patients with EAS a (false) positive ACTH response was found in 2/9 cases (22%) after the CRH test and in 2/5 patients (40%) after the desmopressin test. In the healthy subjects the CRH test was performed in 25 cases and the desmopressin test in 15 cases. The frequency of ACTH response was 52% following CRH and 13% following desmopressin. In the 10 healthy subjects who underwent both tests the ACTH response was significantly greater after CRH than desmopressin. The area under the ROC curve for the ACTH Delta % was significantly different than that occurring by chance following CRH but not desmopressin. The point on the ROC curve closest to 1 corresponded to an ACTH Delta % of 47% (sensitivity 87% and specificity 89%). However, a criterion of 100 % specificity would require an increase in the threshold for the ACTH Delta % to 259%. ROC analysis validated also the use of the ACTH Delta as a method to assess the response to CRH, but not after desmopressin. However, the diagnostic performance of this parameter was reduced in comparison to that of the ACTH Delta %, since the best cut-off for the Delta (6.2 pmol/l) had inferior specificity (79%). The operating characteristics of CRH and desmopressin were worse when considering cortisol responses.

CONCLUSIONS

The present data suggest that the CRH test is more reliable than the desmopressin test in determining the aetiology of Cushing's syndrome. The desmopressin test resulted in a high frequency of false positive results in patients with ectopic ACTH secondary to carcinoid tumours. This finding may be due to the capability of these tumours to express the V3 vasopressin receptor through which desmopressin acts. However, the clinical endocrinologist may be confronted with some disturbing cases which are misdiagnosed because it is almost impossible to set a diagnostic criterion providing complete specificity in the differentiation of (occult) ectopic Cushing's syndrome using either CRH or desmopressin tests.

A new generation IRMA for ACTH with improved specificity: validation in various physiological and pathological conditions

OBJECTIVE

Measurement of plasma ACTH is a key step for the exploration of hypothalamic-pituitary-adrenal disorders. To further improve ACTH recognition a new generation of ACTH IRMA was developed using antibodies directed towards succinylated ACTH (sACTH IRMA).

DESIGN

The usefulness of this assay was compared with that of another commercially available ACTH IRMA assay using intact ACTH (ELSA-ACTH) in various pathophysiological situations: patients with low ACTH plasma levels, high ACTH plasma levels with normal or tumoural pituitaries, or ectopic ACTH syndrome, and pregnant women with high proopiomelanocortin (POMC) plasma levels.

METHODS

All plasma samples were assayed simultaneously with the two different IRMAs. Comparisons were assessed by plotting the results along the theoretical line of identical values, and by the graphical method of Bland and Altman.

RESULTS

In the ELSA-ACTH IRMA, CLIP (or ACTH18-39) showed true cross-reactivity, and alpha-melanocyte-stimulating hormone and purified POMC both interfered and induced falsely lower ACTH results; in the sACTH IRMA no peptide showed any cross-reactivity, and only extremely high values of CLIP (50 000 pg/ml) interfered and induced falsely lower ACTH results. In ACTH hypersecretory syndromes, of tumoural (Cushing's disease, ectopic ACTH secretion) or non-tumoural (Addison's disease, congenital adrenal hyperplasia) origins a good agreement between the two assays was observed except for very high ACTH plasma values (above 1000 pg/ml) and in some tumours where the sACTH IRMA yielded lower results; in some cases, the presence of circulating CLIP, demonstrated by HPLC studies, may contribute to this discrepancy. It is also likely that the calibration of the ELSA-ACTH kit itself generates higher ACTH values. In normal pregnant women both IRMAs gave highly correlated values, yet lower results were obtained with the sACTH IRMA.

CONCLUSION

These data show that the sACTH IRMA has improved qualities of specificity and usefulness for rapid assessment of ACTH plasma levels.

The continuous 7-hour intravenous dexamethasone suppression test in the differential diagnosis of ACTH-dependent Cushing's syndrome

OBJECTIVE

A recent report showing disappointingly low sensitivity and specificity for the oral high dose dexamethasone test in the differential diagnosis of Cushing's syndrome prompted us to re-evaluate the results obtained in our centre using the continuous 7-hour intravenous dexamethasone suppression test for this purpose.

PATIENTS

105 patients with ACTH-dependent Cushing's syndrome were included in this study; 78 with Cushing's disease, 8 with ectopic ACTH-secreting tumours and 19 were classified as 'of unknown aetiology'.

RESULTS

In 74/78 (94.9%) of patients with Cushing's disease and in 3/8 (37.5%) patients with the ectopic ACTH syndrome, a plasma cortisol decrease > 190 nmol/l at 7 h as compared to baseline values was achieved in the continuous 7-hour intravenous dexamethasone suppression test. Using a plasma cortisol decrease > 190 nmol/l at 7 h as compared to baseline values as the cut-off value, the sensitivity and specificity of the continuous 7-hour intravenous dexamethasone suppression test for the diagnosis of Cushing's disease in patients with ACTH-dependent Cushing's syndrome were 94.9% and 62.5%, respectively.

CONCLUSIONS

In patients with ACTH-dependent Cushing's syndrome with a plasma cortisol decrease > 190 nmol/l at 7 h in the continuous 7-hour intravenous dexamethasone suppression test, additional localizing investigations such as bilateral simultaneous inferior petrosal sinus sampling and/or pentetreotide scintigraphy should be performed when no clearly discernible pituitary adenoma is observed on MRI studies. Patients with ACTH-dependent Cushing's syndrome with a plasma cortisol decrease < 190 nmol/l at 7 h in the continuous 7-hour intravenous dexamethasone suppression test should also undergo bilateral simultaneous inferior petrosal sinus sampling and/or pentetreotide scintigraphy to demonstrate the presence of a nonpituitary source of ACTH overproduction.

Marked increase in plasma ACTH with tumor reduction after chemotherapy in ectopic ACTH syndrome

We report on a case of rapid and marked hormone release as a result of rapid tumor reduction due to chemotherapy in a 36-year-old woman with ectopic ACTH syndrome due to small cell lung cancer. Treatment of the cancer with cisplatin and etoposide resulted in an 80% reduction in tumor size on computed tomographic scan within two weeks. Concurrently, plasma ACTH exhibited an unexpected and astonishing increase from 373 pg/ml before treatment to more than 1200 pg/ml. There were no biochemical characteristics observed in tumor lysis syndrome of solid tumors such as azotemia, increased LDH and hyperkalemia. The present case indicates that anticancer chemotherapy instituted in patients with ectopic ACTH syndrome could result in an acute increase of plasma ACTH and exacerbation of hypercortisolism, similar to tumor lysis syndrome, which is a potentially fatal complication following anti-cancer chemotherapy.

Cyclical Cushing's syndrome--a trap for the unwary

A woman with cyclical Cushing's syndrome due to periodic hormonogenesis from a corticotropin (ACTH) secreting pituitary adenoma is discussed. This patient presented with acute steroid-induced psychosis but she was found to have subtle cushingoid features that went undetected for two years. Laboratory evaluation for Cushing's syndrome showed incongruous results due to periodic ACTH production by the tumour. Cyclical Cushing's syndrome may be an under-recognised phenomenon and incorrect interpretation of investigative results may lead to wrong tumour localisation and inappropriate surgery. This case highlights the subtleties and complexities that one may encounter in the diagnostic evaluation of patients with Cushing's syndrome, and emphasises that the laboratory results must always be interpreted in the appropriate clinical context.

A critical analysis of the value of simultaneous inferior petrosal sinus sampling in Cushing's disease and the occult ectopic adrenocorticotropin syndrome

The clinical, biochemical, and radiological features of pituitary ACTH-dependent Cushing's syndrome (CS) [Cushing's disease (CD)] are often indistinguishable from those of occult ectopic ACTH-dependent CS (oEAS). We have evaluated, retrospectively, the results of simultaneous bilateral inferior petrosal sinus (IPS) ACTH sampling before and after CRH stimulation in 128 patients with ACTH-dependent CS: 107 patients with CD, 6 with oEAS, 1 with an adrenal adenoma, 1 with a pituitary gangliocytoma, and 1 with Nelson's syndrome; while, in the remaining 12, the source remains unclear. One hundred seven patients received human-sequence CRH (hCRH), and 11 received ovine CRH; another 6 patients underwent stimulation with desmopressin and hCRH, and 4 with desmopressin alone. A successful bilateral IPS catheterization and sampling (IPSCS) rate of 87.5% was obtained only after considerable experience had been gained. Sixty-nine patients with CD underwent successful bilateral IPSCS: the IPS-to-peripheral ratio of plasma ACTH value (IPS/P) rose from 9.5 +/- 1.4 to a maximum ratio of 55.8 +/- 7.5 in 67 patients, after CRH stimulation. The maximum ratio was obtained at 5 min in 60 of the 69 patients with CD; however, all 69 patients obtained a ratio of more than 2, at that time. In contrast, the 6 patients with occult ACTH-secreting neoplasms had a maximal IPS/P ratio of 1.3 +/- 0.16, and this did not change after CRH stimulation. A bilateral IPS/P ratio more than 2, obtained 5 min after CRH stimulation, had a sensitivity of 97% and a specificity of 100% in diagnosing CD. Two patients with proven active CD had an IPS/P ratio of less than 2. After successful bilateral IPSCS, the gradients between the IPS ACTH concentrations [IPS ACTH gradient (IPSG)] of more than 1.4, at 5 min after CRH stimulation, had a sensitivity of 83% in correctly lateralizing the pituitary microadenoma, compared with 72% sensitivity for magnetic resonance imaging (MRI) scanning. Furthermore, when IPSG and MRI findings were contradictory, IPSG was more often correct than MRI scanning. Although oEAS is a relatively uncommon cause of ACTH-dependent hypercortisolism (5.5% in our series), the accurate diagnosis of ACTH-dependent CS and localization of an intrapituitary microadenoma requires bilateral IPSCS with CRH stimulation, provided that the appropriate technical experience is available. hCRH is as effective a secretagogue as ovine CRH, and either may be used. The value of the combination of CRH and desmopressin stimulation requires more detailed investigation.

Long-term medical treatment of ectopic ACTH syndrome

BACKGROUND

The morbidity of hypercortisolemia due to ectopic production of ACTH by various tumors may be greater than the morbidity of the tumor itself.

METHODS

We report three cases of long-term treatment of ectopic ACTH syndrome due to metastatic bronchial carcinoid, islet cell carcinoma, and malignant thymoma tumors. Clinical and biochemical eucortisolemia was achieved in each case and was sustained from 24 to 55 months. We review the therapeutic options and their reported efficacy.

RESULTS

Cessation of therapy resulted in recurrence of hypercortisolemia in each case, showing the effectiveness of therapy.

CONCLUSION

Long-term treatment of ectopic ACTH-induced hypercortisolemia by blocking adrenal steroidogenesis is clinically effective and well tolerated.

A very high dose dexamethasone suppression test for differential diagnosis of Cushing's syndrome

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.

[Ectopic ACTH secretion: a heterogeneous entity]

OBJECTIVES

ACTH-secreting non-pituitary tumors are a rare cause of Cushing's disease. We report the clinical course, prognostic aspects and molecular analysis data in three patients for whom the diagnosis was confirmed but who had variable clinical features and laboratory results.

CASE REPORTS

Patient n degree 1 had severe hypercorticism which rapidly progressed to death 13 months after diagnosis. In patient n degree 2, signs of hypercorticism severe, leading to death 5 years after discovery of the causal carcinoid tumor. Patient n degree 3 had moderate hypercorticism and has survived for more than 25 years.

DISCUSSION

These 3 ectopic tumors are representative examples of a wide range of possible ACTH-secreting ectopic tumors. In highly malignant poorly-differentiated tumors such as small-cell anaplastic carcinomas, ACTH production is aberrant and poorly controlled, and thus not particularly effective. At the other extreme, typical benign bronchial carcinomas have a high degree of neuroendocrine differentiation and secrete ACTH in a well-controlled manner difficult to distinguish from corticotropic adenomas, further exaggerating the diagnostic pitfalls.

Effect of desmopressin on ACTH and cortisol secretion in states of ACTH excess

OBJECTIVE

To assess the ability of desmopressin administration to stimulate ACTH/cortisol secretion in patients with Cushing's disease, either before or after surgery, and in patients with other states characterized by ACTH hypersecretion, and to compare the results with those obtained after CRH testing.

DESIGN AND SUBJECTS

Plasma ACTH and serum cortisol levels were evaluated after the administration of desmopressin (10 micrograms i.v.), CRH (1 microgram/kg i.v.) and saline on different days in 17 patients with Cushing's disease, 1 with occult ectopic ACTH syndrome, 5 with Addison's disease, 3 who had been bilaterally adrenalectomized for Cushing's syndrome and 4 normal subjects. After pituitary adenomectomy desmopressin and CRH were administered again to 13 of the patients who had undergone pituitary surgery for their Cushing's disease.

RESULTS

In 16 patients with Cushing's disease with microadenoma a positive ACTH/cortisol rise occurred in 11 patients after both desmopressin and CRH, 2 other patients were responsive only to desmopressin and 2 only to CRH, while in 1 patient equivocal responses to both tests were found. The persistence of a hormonal response to desmopressin after pituitary adenomectomy for Cushing's disease correlated with unsuccessful surgery, while, contrary to CRH, absent ACTH/cortisol rises were found in cured patients 1 and 12 months after operation. In 1 patient suspected for ectopic ACTH hypersecretion, desmopressin and CRH administration did not cause any ACTH/cortisol rise. Significant ACTH rises occurred after both desmopressin and CRH testing in patients with Addison's disease. All the 3 patients adrenalectomized for Cushing's syndrome showed a rise of ACTH levels after CRH, while a similar response after desmopressin occurred in only one of them.

CONCLUSIONS

Desmopressin is able to stimulate ACTH and hence cortisol release in Cushing's disease. It may be a useful test in patients with doubtful responses to CRH test, in those exhibiting responses to CRH indistinguishable from those of normal subjects and in the postoperative follow-up of Cushing's disease. In some patients with abolished or reduced cortisol feed-back at hypothalamic-pituitary level the sensitivity of normal corticotrophs to desmopressin is enhanced.

High plasma proopiomelanocortin in aggressive adrenocorticotropin-secreting tumors

A specific propiomelanocortin (POMC) immunoradiometric assay was developed using antibodies directed against ACTH and beta-endorphin (beta end). Partially purified standard POMC was prepared from the human small cell lung carcinoma cell line DMS-79 culture medium. Ten units (U) POMC had the same displacement ability as one pg beta end in a C-terminal beta end radioimmunoassay and thus were close if not equal to 10 pg POMC. This POMC assay was used to investigate patients with ACTH-dependent Cushing's syndrome. Plasma POMC was undetectable (< 60 U/mL) in 17 normal controls and in 4 patients with Addison's disease (concomitant ACTH plasma levels between 362 and 1058 pg/mL). Forty-two patients with Cushing's disease were studied, either before (n = 25) or after (n = 17) bilateral adrenalectomy: 7 patients with highly invasive macroadenomas had high POMC plasma levels, between 240 and 4200 U/ml (concomitant ACTH plasma levels between 77 and 5730 pg/mL); 35 patients, including one with an invasive macroadenoma, had undetectable POMC plasma levels (concomitant ACTH plasma levels between 31 and 2820 pg/mL). Among 20 patients with histologically proven ectopic ACTH syndrome, 16 had high POMC plasma levels, between 80 and 8000 U/mL (concomitant ACTH plasma levels between 45 and 9265 pg/mL); all those tumors were malignant, and the highest POMC/ACTH plasma levels ratios (taken as an index of altered POMC processing) were observed in the 3 patients with small cell carcinomas of the lung; in one of these patients, ACTH and POMC plasma levels both decreased during the course of chemotherapy, in parallel with the reduction of the tumoral mass. Four patients with ectopic ACTH syndrome had undetectable POMC plasma levels (concomitant ACTH plasma levels between 78 and 335 pg/mL): they were all typical bronchial carcinoids. These data show that high POMC plasma level is neither specific for nor constant in ectopic ACTH syndrome. Rather it should be considered as a marker of tumor aggressivity, in pituitary- and non-pituitary tumors. Its diagnostic help appears limited for the most frequent cause of occult ectopic ACTH syndrome, the typical bronchial carcinoids.

A comparison of the overnight and the standard metyrapone test for the differential diagnosis of adrenocorticotrophin-dependent Cushing's syndrome

OBJECTIVE

We wished to develop optimal criteria for interpreting the single-dose overnight metyrapone test and to compare the diagnostic efficiency of the overnight and the standard 6-dose metyrapone tests for the differential diagnosis of ACTH-dependent Cushing's syndrome.

DESIGN

Retrospective pilot study based on all patients who completed both metyrapone tests and whose diagnoses were subsequently confirmed surgically.

PATIENTS

Sixty-three patients, 57 with pituitary tumours and 6 with ectopic ACTH syndrome, were studied.

MEASUREMENTS

The sensitivity and specificity were determined using stimulation of plasma 11-deoxycortisol and suppression of plasma cortisol as endpoints for the overnight test and stimulation of urine 17-hydroxysteroid and plasma 11-deoxycortisol as endpoints for the standard test. The lest response that gave the highest sensitivity for the diagnosis of Cushing's disease, with 100% specificity, was determined for each test endpoint.

RESULTS

Both the stimulation of plasma 11-deoxycortisol and the suppression of plasma cortisol were expressed as the ratio of the post-metyrapone value to baseline. A plasma 11-deoxycortisol ratio > than 220 or a plasma cortisol ratio > 0.6 was associated with 100% specificity for diagnosis of Cushing's disease by the overnight test. When these two criteria were combined, the sensitivity was 65%, which was significantly higher than that obtained using either steroid alone: 42% for both plasma 11-deoxycortisol and plasma cortisol. The sensitivity of 65% for the overnight test, at 100% specificity, was nearly identical to that of the standard test in the same patients: 67% for the combined criterion of > 70% stimulation of urine 17-hydroxysteroid or > 480-fold increase of plasma 11-deoxycortisol. When the criteria for both the overnight and standard tests were combined, the sensitivity increased to 84%, which was higher than that obtained using the criteria for either test alone (P < 0.02).

CONCLUSION

The single-dose overnight metyrapone test, which can be performed in 24 hours and which avoids the disadvantages associated with timed urine collections, has a nearly identical sensitivity (for a specificity of 100%) as the 6-dose standard metyrapone test for the diagnosis of Cushing's disease. Furthermore, the diagnostic performance of a criterion that combines the results of both tests is significantly better than the best criterion for either test alone.

Correction of metabolic alkalosis by potassium chloride in ectopic adrenocorticotropic hormone syndrome

A 57-year-old white man presented with metabolic alkalosis, hypokalemia (pH 7.58, HCO3 >50 mEq/L, serum K 1.8 mEq/L) and hypertension. The initial evaluation was significant for markedly elevated serum cortisol and adrenocorticotropic hormone (ACTH) level; neither hormone showed circadian rhythm or suppression with high-dose dexamethasone. Perihilar and supraclavicular masses were found to consist of undifferentiated small cell carcinoma. Ectopic ACTH syndrome was diagnosed. In spite of progressively rising hormone levels (ACTH, 723 pg/dL; and cortisol, 212 microgram/dL), his severe metabolic alkalosis was largely corrected by aggressive treatment with potassium chloride alone. Possible mechanisms of these clinical findings are discussed.

Ouabainlike compound in hypertension associated with ectopic corticotropin syndrome

Molecular mechanisms related to sodium retention have been implicated in the pathogenesis of hypertension. It is unclear how sodium retention leads to a rise in blood pressure, but ouabainlike compound may act as a final common pathway in sodium-induced hypertension. In ectopic corticotropin syndrome, hypertension has been attributed to cortisol inactivation overload, giving rise to mineralocorticoid-type hypertension. We sequentially measured plasma and urinary levels of ouabainlike compound over 2 months to evaluate its role in the hypertensive mechanisms in a 64-year-old man with this syndrome caused by lung cancer. His data included hypokalemia and increased cortisol concentrations, corticotropin levels, and urinary 17-hydroxycorticosteroid excretion. Plasma renin activity was suppressed. Plasma and urinary levels of ouabainlike compound were markedly increased concomitantly with high blood pressure. The maximum plasma level was 40-fold the normal range of the subject. After chemotherapy, ouabainlike compound levels gradually decreased in parallel with the decline in blood pressure and rise in potassium concentration. A correlation was observed between plasma and urinary levels of ouabainlike compound (P < .05). Plasma and urinary levels of ouabainlike compound correlated with systolic (P < .01) and diastolic (P < .05) pressures, respectively. The peak of ouabainlike compound in plasma and urine coincided with that of authentic ouabain on high-performance liquid chromatography. Ouabainlike compound derived from urine inhibited [3H]ouabain binding to human erythrocytes. These findings suggest that ouabainlike compound with biological activity could partly account for hypertension in ectopic corticotropin syndrome.

Ectopic ACTH syndrome: redefinition and case report

A case is reported which supports the principle that ACTH precursors best characterise so-called ectopic ACTH-syndrome, which should therefore more accurately be referred to as ectopic ACTH-precursor syndrome.

Pseudo-tumours of the thymus after correction of hypercortisolism in patients with ectopic ACTH syndrome: a report of five cases

We report the cases of four patients with occult, and one patient with overt, ectopic ACTH syndrome. Cushing's syndrome was cured by removal of the ACTH secreting tumour, op'DDD, ketoconazole or bilateral adrenalectomy. Six to 14 months after remission of hypercortisolism, follow-up computed tomography or magnetic resonance imaging of the thorax revealed in all five patients an anterior mediastinal mass 3-5 cm in length that suggested a thymic carcinoma. Exploratory thoracotomy was performed in four cases and allowed the removal of an enlarged, but normal, thymus. Histological examination revealed no tumour but showed benign thymic hyperplasia with negative immunostaining for ACTH. Thymic enlargement spontaneously disappeared 11 months after its demonstration in the patient who did not undergo thoracotomy. The mechanism of this abnormality is thought to be thymic depletion resulting from high plasma cortisol concentrations followed by 'rebound' thymic hyperplasia when cortisol levels fall. Physicians involved in the management of patients with Cushing's syndrome must be aware of this entity in order to avert a diagnostic thoracotomy.

Ketoconazole in the management of paraneoplastic Cushing's syndrome secondary to ectopic adrenocorticotropin production

PURPOSE

To evaluate the safety and efficacy of ketoconazole treatment in the management of patients with paraneoplastic Cushing's syndrome (CS) secondary to ectopic adrenocorticotropin (ACTH) production by malignant neoplasms (ECS).

PATIENTS AND METHODS

A retrospective chart review was undertaken for 15 consecutive patients with ECS treated with ketoconazole. Strict criteria were defined for diagnosis of ECS and for clinical, biochemical, and hormonal responses.

RESULTS

There were four women and 11 men with a median age of 59 years (range, 44 to 84). Eleven patients had primary lung cancer (nine small-cell [SCLC], one mixed SCLC/non-SCLC, and one non-SCLC); two had carcinoid tumors (one bronchial, one pancreatic); one had hepatocellular carcinoma; and one had medullary carcinoma of the thyroid. Eight patients had ECS diagnosed at tumor presentation. Clinical findings included proximal muscle weakness (n = 10), peripheral edema (n = 8), and hypertension (n = 8). Biochemical abnormalities included hypokalemia (n = 14), metabolic alkalosis (n = 13), and new or worsened diabetes mellitus (n = 10). Patients received ketoconazole in dosages of 400 to 1,200 mg/d titrated by changes in urinary free-cortisol (UFC) levels for a median duration of 26 days (range, 3 to 1,059), and nine also received chemotherapy with ketoconazole. Hypokalemia, metabolic alkalosis, diabetes mellitus, and hypertension improved in the majority of patients. Ten patients had a hormonal response, with seven complete responses (median duration, 25 days; range, 6 to 989). The occurrence of symptomatic hypoadrenalism was definite in three patients and probable in one. Most patients died of progressive malignant disease accompanied by escape from hormonal control by ketoconazole. The median survival duration of the group was 19 weeks (range, 1 to 154).

CONCLUSION

Ketoconazole results in biochemical and hormonal improvement for most patients with ECS. It has few adverse effects, but may impair the cortisol response to stress. For that reason, replacement corticosteroids should be considered for patients with hormonal response, and moderate- to high-dose corticosteroids should be given for any potential stress situations. The ultimate control of the syndrome is dependent on successful treatment of the underlying tumor.

Dissociation of adrenal androgen and cortisol secretion in Cushing's syndrome

OBJECTIVES

While ACTH may modulate adrenal androgen production, there is evidence that other factors are required. Cushing's disease and ectopic ACTH secretion provide a little utilized opportunity to examine adrenal androgen levels in conditions of ACTH excess. We have compared plasma cortisol values with plasma levels of androstenedione, dehydroepiandrosterone (DHEA), DHEA-sulphate (DHEAS), testosterone and an index of free testosterone, the testosterone/sex hormone binding globulin ratio, prior to treatment in patients with Cushing's syndrome.

PATIENTS AND MEASUREMENTS

Plasma from 15 adult patients with Cushing's disease and three adults with the ectopic ACTH syndrome was obtained prior to treatment and submitted to specific immunoassays for the measurement of the above steroids.

RESULTS

Plasma cortisol values of 15 patients with Cushing's disease (range 326-1140 nmol/l, normal range 190-690 nmol/l) were elevated in 9; in contrast, plasma androstenedione (4.1-11.3 nmol/l, normal range, men 2.1-7.7, women 3.3-9.9 nmol/l) was elevated in only two patients, plasma DHEAS (3.3-17.8 mumol/l, normal range, men 4.5-18.4, women 3.5-11.8 mumol/l) was elevated in only 4 patients and plasma DHEA (4.8-45.2 nmol/l, normal range 11-48 nmol/l) was normal or low in all 15 patients. Plasma androstenedione was markedly elevated (74 nmol/l) in one of three patients with ectopic ACTH syndrome, moderately elevated in another, and normal in the third patient. In contrast, plasma DHEA and DHEAS levels were suppressed in the patient with the highest androstenedione level and low or normal in the other two patients.

CONCLUSIONS

These data suggest that ACTH alone does not control adrenal androgen secretion. The data also suggest that variability in the processing of proopiomelanocortin (the precursor of ACTH and related peptides) occurring in Cushing's disease and ectopic ACTH syndrome may account for differences in the relation of cortisol to androgens observed between the disorders and when compared to that in normal subjects.

[Selective catheterization of the inferior petrosal sinus]

The inferior petrosal sinus is a dura sinus which traverses laterally and dorsally from the dorsal aspect of the cavernous sinus. It represents the nearest catheterization point for blood sampling from the pituitary gland. Inferior petrosal sinus venous sampling is used for diagnosis and lateralization of ACTH-secreting and growth hormone-producing hypophyseal adenomas. It is also used in the differential diagnosis of ectopic production of ACTH or other similar peptides. We briefly describe the anatomy of the inferior petrosal sinus and the catheterization technique, based on our experience from 15 patients. The endocrinological results are published in a separate article.

Spontaneous vulvar necrotizing fasciitis in Cushing's syndrome

Necrotizing fasciitis is a potentially fatal condition, and the prognosis is worsened by immunosuppression. We describe what appears to be the first reported case of spontaneous vulvar necrotizing fasciitis occurring in a woman with uncontrolled hypercortisolism due to an ACTH-secreting thymic carcinoid tumor.

Severe diarrhea and Cushing's syndrome from an atypical bronchial carcinoid

Bronchial carcinoids are uncommon pulmonary tumors, considered neuroendocrine in origin and all types may produce various hormones. We describe a young woman with a 2-year history of radiographically stable atypical bronchial carcinoid, ectopic ACTH production, and a markedly elevated calcitonin level. The Cushing's syndrome and diarrheal illness were due to the ectopic hormones.

The overnight dexamethasone test is the procedure of choice in screening for Cushing's syndrome

This study was undertaken to examine the performance of the overnight dexamethasone test, i.e., plasma cortisol level at 8-9 AM following dexamethasone 1 mg by mouth at midnight, in screening for Cushing's syndrome. The participants included 19 patients with Cushing's syndrome (17 with Cushing's disease, 1 with adrenal carcinoma, and 1 with ectopic ACTH syndrome) and 96 patients in whom the possibility of Cushing's syndrome was raised but who did not have the disorder. Utilizing our original very conservative cutoff point of plasma 100 nmol/L (3.62 micrograms/dL) above which Cushing's syndrome was suspected, the sensitivity of the test was 100% but the false positive rate was an unsatisfactory 12.5%. However, the lowest plasma cortisol level achieved following the overnight dexamethasone test in patients with Cushing's syndrome was 259 nmol/L (9.39 micrograms/dL). A plasma cortisol cutoff point of 250 nmol/L (9.06 micrograms/dL) yielded no false negatives and the false positive rate fell to 6.25%. Using a cutoff point of 200 nmol/L (7.24 micrograms/dL) the false positive rate was 7.3%. These performance characteristics of the overnight dexamethasone test compare very favorably with the reported experience of all other screening procedures for Cushing's syndrome including the urinary free cortisol excretion rate and the 48 h dexamethasone test, while the overnight dexamethasone procedure is the simplest for both patients and medical personnel. Since it is possible that some very unusual patients may suppress to plasma cortisol levels lower than that seen in the present study, we now recommend the overnight dexamethasone test using a plasma cortisol cutoff point of 200 nmol/L as the procedure of choice when screening for patients with Cushing's syndrome.

ACTH precursors characterize the ectopic ACTH syndrome

OBJECTIVE

ACTH is secreted by the pituitary following processing of larger molecular weight precursors, proopiomelanocortin and pro-ACTH. Ectopic ACTH syndrome refers to the secretion of ACTH by non-pituitary tumours, but the predominant circulating form of proopiomelanocortin-related peptides remains unclear.

PATIENTS

Fifteen patients with ectopic ACTH syndrome were compared to 20 patients with pituitary-dependent Cushing's syndrome, 22 patients with small cell lung carcinoma but no evidence of Cushing's syndrome, and 25 controls.

DESIGN AND MEASUREMENTS

Measurement of plasma ACTH and ACTH precursors using specific monoclonal-based immunoradiometric assays at 0900 h and, in five patients with ectopic ACTH syndrome, at 15-minute intervals for 6-24 hours.

RESULTS

ACTH precursors were grossly elevated in patients with ectopic ACTH syndrome (median 2194, range 139-18000 pmol/l) compared to patients with Cushing's disease (median 33, 8-73 pmol/l, P < 0.001), patients with small cell lung carcinomas (38, 8-117 pmol/l, P < 0.001) and controls (26, 10-39 pmol/l, P < 0.001). ACTH levels were also elevated in ectopic ACTH syndrome (0900 h median 34, 11-152 pmol/l) compared to patients with Cushing's disease (0900 h median 8, 3-19 pmol/l), but not to the same degree as ACTH precursors. In contrast with Cushing's disease, ACTH was secreted in a non-pulsatile fashion. ACTH precursors but not ACTH itself correlated with plasma cortisol in patients with ectopic ACTH syndrome (r = 0.65, P < 0.05). Chromatographic analysis of plasma from a patient with ectopic ACTH syndrome confirmed ACTH precursors and not ACTH to be the predominant circulating form. With the cross-reactivity of proopiomelanocortin and pro-ACTH in the ACTH IRMA of < 1 and < 10% respectively, ACTH precursors could represent all the ACTH immunoreactivity in patients with ectopic ACTH syndrome.

CONCLUSIONS

Ectopic 'ACTH' is characterized by aberrant processing of proopiomelanocortin and should be more accurately referred to as 'ectopic ACTH precursor syndrome'.

Effective reversibility of the signs and symptoms of hypercortisolism by bilateral adrenalectomy

BACKGROUND

The long-term outcome of bilateral adrenalectomy in the management of patients with Cushing's syndrome has not been previously well studied.

METHODS

We reviewed our long-term results in 34 patients treated with bilateral adrenalectomy between 1983 and the present. Fourteen presented with occult or metastatic ectopic adrenocorticotropic hormone (ACTH) syndrome, 10 with failed treatment of Cushing's disease, five with primary micronodular and four with massive macronodular adrenocortical disease and one with indeterminate cause of Cushing's syndrome.

RESULTS

All patients underwent bilateral adrenalectomy. Of 19 patients who required antihypertensive medications before operation, 15 (79%) had significant improvement and were either off all antihypertensive medication or required less medication after operation. Of 7 patients who required medications for diabetes mellitus, after operation 6 (86%) required no medication or changed from injections to oral hypoglycemic agents. Of 9 patients with mood changes or depression, the symptoms of 8 (88%) resolved. Of 29 patients with documented weight gain, 23 (79%) showed marked weight loss. Of 13 hirsute patients, 10 (77%) had resolutions of symptoms. Of 21 patients with complaints of fatigue, the symptoms of 16 (76%) resolved. Of 8 women with amenorrhea, 6 (75%) had resolution of symptoms. Each patient in the primary adrenocortical disease group, except one with residual fatigue, had complete resolution of his or her symptoms. There was no difference in resolution of symptoms between the ectopic ACTH and Cushing's disease groups. Six patients died: in the ectopic ACTH group one died of suicide at 1 month, and four of metastatic tumor at 9, 24, 25, and 48 months, and the patient with macronodular adrenocortical hyperplasia died of a myocardial infarction at 30 months. The remainder of the patients have been followed for a mean of 32 months (3 to 67 months). None of the patients had any evidence of recurrent hypercortisolism.

CONCLUSIONS

We conclude that bilateral adrenalectomy is a safe, effective, and long-lasting method to ameliorate the devastating signs and symptoms of hypercortisolism in patients with Cushing's syndrome.

Discrimination between beta-endorphin and beta-lipotrophin in human plasma using two-site immunoradiometric assays

OBJECTIVE

We wished to discriminate between the opioid peptide beta-endorphin (beta-EP) and its non-opioid precursor beta-lipotrophin (beta-LPH) in normal subjects and patients with ACTH-related disorders.

DESIGN

We produced monoclonal antibodies to beta-EP and beta-LPH for the development of two-site immunoradiometric assays (IRMAs) which specifically quantitate beta-EP and beta-LPH.

PATIENTS

Samples were obtained from patients with a range of ACTH-related disorders and compared with 18 normal subjects. Peptide levels were also compared in six patients with Cushing's syndrome undergoing bilateral inferior petrosal sinus sampling with corticotrophin releasing hormone administration.

MEASUREMENTS

In the beta-EP IRMA, antibody 6B2, specific for beta-EP 18-27, is radiolabelled and antibody 2E10, recognizing beta-EP 1-5, is coupled to Sephacryl S-300 as solid phase. The IRMA is specific for beta-EP (beta-LPH cross-reacts < 0.02%), has a detection limit of 1.4 +/- 0.7 pmol/l (n = 7) and has a within-assay coefficient of variation of < 10% between 4.9 and 1200 pmol/l. In the beta-LPH IRMA, antibody 6B2, which recognizes an epitope common to beta-LPH and beta-EP, is radiolabelled and paired with solid-phase antibody 5C11 which recognizes beta-LPH 39-56. The binding site of this antibody ensures that beta-EP cannot be measured in the beta-LPH assay. The detection limit is 0.8 +/- 0.1 pmol/l (n = 9) and the within-assay coefficient of variation is < 10% at concentrations 1.7-870 pmol/l.

RESULTS

In normal subjects, beta-EP and beta-LPH levels were < 1.4-1.7 pmol/l (< 5-6 ng/l) and 2.5-6.7 pmol/l (29-77 ng/l) at 0930 h and < 1.4-1.7 pmol/l (< 5-6 ng/l) and 1.9-4.5 pmol/l (22-49 ng/l) at 1600 h, respectively. In patients with ACTH-related pathologies concentrations of beta-EP and beta-LPH paralleled those of ACTH. The ratio of beta-LPH:beta-EP in plasma varied between 3.2:1 and 38:1 in these patients demonstrating that beta-LPH is the major circulating peptide derived from the C-terminal of pro-opiomelanocortin in man. However, in two patients undergoing bilateral inferior petrosal sampling with corticotrophin releasing hormone for diagnosis of Cushing's disease beta-EP concentrations increased rapidly during the first 5 minutes of the test, resulting in a sharp decrease in the beta-LPH: beta-EP ratio. These results suggest that beta-EP is preferentially released in response to acute corticotrophin releasing hormone stimulation.

CONCLUSIONS

It is concluded that two-site IRMAs for beta-EP and beta-LPH provide an easy approach to study the dynamic changes in processing of beta-LPH to beta-EP.

Mineralocorticoid excess and inhibition of 11 beta-hydroxysteroid dehydrogenase in patients with ectopic ACTH syndrome

OBJECTIVE

11 beta-Hydroxysteroid dehydrogenase protects renal mineralocorticoid receptors from cortisol by converting cortisol to inactive cortisone. We hypothesize that 11 beta-dehydrogenase is inhibited by ACTH, providing a mechanism whereby cortisol induces hypokalaemic alkalosis in ectopic ACTH syndrome.

DESIGN/MEASUREMENTS

The principal sources of plasma cortisone were assessed by selective venous catheterization with measurement of cortisol and cortisone by radioimmunoassays. The effect of ACTH on peripheral plasma cortisol/cortisone ratio was assessed in healthy volunteers during circadian rhythm, insulin induced hypoglycaemia, and infusions with exogenous ACTH or cortisol. In patients with Cushing's syndrome plasma cortisol/cortisone ratios were related to plasma potassium, corticosterone, and 11-deoxycorticosterone concentrations.

PATIENTS

Catheterization was performed in 24 patients with valvular or ischaemic heart disease. Cushing's syndrome patients included: 15 with pituitary adenoma; two with adrenal adenoma; and nine with ectopic ACTH secretion.

RESULTS

Plasma cortisol/cortisone ratios were low in renal vein and high in hepatic vein. In healthy volunteers plasma cortisone increased during cortisol infusion but did not change with increases in endogenous or exogenous ACTH. Plasma cortisol/cortisone ratios were higher in ectopic ACTH syndrome than in other forms of Cushing's syndrome. However, the cortisol/cortisone ratio was no better a predictor of hypokalaemia than the levels of 11-deoxycorticosterone or corticosterone.

CONCLUSIONS

Peripheral conversion of cortisol to cortisone occurs mainly in the kidney and is inhibited by ACTH. In ectopic ACTH syndrome the characteristic mineralocorticoid excess can be accounted for by a combination of increased secretion of cortisol, corticosterone and of 11-deoxycorticosterone and decreased inactivation of cortisol and corticosterone by 11 beta-dehydrogenase.

Surgical strategy in the management of non-small cell ectopic adrenocorticotropic hormone syndrome

BACKGROUND

Non-small cell ectopic adrenocorticotropic hormone (ACTH) syndrome is a rare cause of hypercortisolism that may require surgery for either curative resection or palliative adrenalectomy.

METHODS

We report our surgical experience with 41 patients with ectopic ACTH syndrome and no evidence of small cell lung cancer at initial evaluation.

RESULTS

All 41 patients had documented hypercortisolism secondary to ectopic production of ACTH. Based on imaging study results, we determined that 21 patients had localized/resectable disease; eight patients had metastatic disease, and 12 patients had occult disease at examination. Of the 21 patients with localized disease, 16 (76%) were cured of ectopic ACTH by surgery (15 bronchial carcinoid, one pheochromocytoma). Patients with bronchial carcinoid had the greatest probability for cure of ectopic ACTH syndrome, and patients with thoracic primary tumor were more likely to be cured than patients with abdominal primaries. Of the eight patients who had metastatic disease, none were cured of the disease; five patients underwent bilateral adrenalectomy, and three patients were given medical therapy. Only one patient was alive after 5 years. Of the 12 patients who had occult disease, four patients were eventually cured of the disease (three bronchial carcinoid, one thymic carcinoid); one patient died of disease (small cell lung cancer), and seven patients still have occult disease. Nine of 12 patients with occult disease underwent bilateral adrenalectomy for surgical management of hypercortisolism.

CONCLUSIONS

This study suggests that the most common primary focus of ectopic ACTH production is within the thorax with 25 of 34 (74%) identifiable tumors originating within either the thymus or bronchus. Adrenalectomy offers excellent palliation of hypercortisolism secondary to either occult or metastatic disease. Patients who initially have localized disease usually have bronchial carcinoids and have a high probability of cure with surgical resection (81%).

Cushing's syndrome associated with lung tumors

The production of corticotropin or corticotropin-releasing factor by non-pituitary, non-adrenal tumors may rarely be associated with an overt clinical expression of hypercortisolism. Recent studies have emphasized the importance of careful thoracic evaluation when such ectopic hormone secretion is suspected.

Short and long-term responses to metyrapone in the medical management of 91 patients with Cushing's syndrome

OBJECTIVE

To analyse the clinical and biochemical effects of metyrapone in the treatment of Cushing's syndrome.

DESIGN

An evaluation of the standard clinical practice at one institution.

PATIENTS

Ninety-one patients with Cushing's syndrome: 57 pituitary-dependent Cushing's disease, 10 adrenocortical adenomas, six adrenocortical carcinomas and 18 ectopic ACTH syndrome.

MEASUREMENTS

The acute response to metyrapone was assessed by measuring cortisol, 11-desoxycortisol and ACTH at 0, 1, 2, 3, 4 hours after a test dose of 750 mg of metyrapone. The longer-term effect of metyrapone was judged by measuring serum cortisol at 0900, 1200, 1500, 1800, 2100 and sometimes 2400 h and calculating a mean.

RESULTS

A test dose of 750 mg of metyrapone decreased serum cortisol levels within 2 hours in all groups of patients and this effect was sustained at 4 hours. At the same time, serum 11-desoxycortisol levels increased in all patients, while plasma ACTH increased in patients with pituitary Cushing's disease and the ectopic ACTH-syndrome. Fifty-three patients with Cushing's disease were followed on short-term metyrapone therapy (1 to 16 weeks) before other more definitive therapy. Their mean cortisol levels (median 654 nmol/l, range 408-2240) dropped to the target range of less than 400 nmol/l in 40 patients (75%) on a median metyrapone dose of 2250 mg/day (range 750-6000). Metyrapone was given long term in 24 patients with Cushing's disease who had been given pituitary irradiation, for a median of 27 months (range 3-140) with adequate control of hypercortisolaemia in 20 (83%). In 10 patients with adrenocortical adenomas and six with adrenocortical carcinomas, metyrapone in a median dose of 1750 mg/day (range 750-6000) reduced their mean cortisol levels (median 847 nmol/l, range 408-2000) to less than 400 nmol/l in 13 patients (81%). In 18 patients with the ectopic ACTH-syndrome the 'mean cortisol levels', obtained from five or six samples on the test day (median 1023 nmol/l, range 823-6354) were reduced to less than 400 nmol/l in 13 patients (70%), on a median dose of 4000 mg/day (range 1000-6000). Reduction of cortisol levels was clearly associated with clinical and biochemical improvement. The medication was well tolerated. Transient hypoadrenalism and hirsutism were unusual but were the most common side-effects.

CONCLUSIONS

In our experience metyrapone remains a most useful agent for controlling cortisol levels in the management of Cushing's syndrome of all types.

Palliative therapy of an ectopic Cushing's syndrome due to a metastatic carcinoid tumor

The case of a 39-year-old patient with ectopic Cushing's syndrome due to a metastatic carcinoid tumor is presented. Palliative therapy consisting of 800 mg ketoconazole and 0.3 mg SMS 201-995/die resulted in clinical remission and correction of hypokalemia and hypercortisoluria. Combined therapy was clearly superior to monotherapy with ketoconazole or SMS 201-995, respectively. Side effects were not observed, the tumor masses remained unchanged throughout the observation period of now 19 months.

An evaluation of the distinction of ectopic and pituitary ACTH dependent Cushing's syndrome by clinical features, biochemical tests and radiological findings

The efficiency of various laboratory and radiological investigations in the differentiation of ectopic from pituitary dependent Cushing's syndrome was studied, based on findings in 23 patients with verified Cushing's disease and seven patients with the ectopic ACTH syndrome. Clinical features strongly favouring the ectopic type were male sex and history for less than 18 months. Basal biochemical features strongly indicating the ectopic syndrome included plasma K+ less than 3.0 mmol/l and HCO3 greater than 30 mmol/l; serum cortisol at 9 a.m. or midnight of greater than 800 nmol/l; urine free cortisol greater than 1300 nmol/24 hours; plasma ACTH greater than 100 ng/l. In the high-dose dexamethasone suppression test, suppression by less than 50 per cent of 9 a.m. serum cortisol, urine free cortisol or 17-oxogenic steroids was usually indicative of an ectopic source of ACTH. A mean suppressed value of greater than 450 nmol/l for the 9 a.m. and midnight cortisol combined occurred in all of those with the ectopic syndrome, but in none of the 23 patients with Cushing's disease. For urine free cortisol, a mean suppressed value of less than 1000 nmol/24 hours was found in all patients with Cushing's disease, but in none of those in the ectopic group. In the metyrapone test, there was an increase of less than or equal to 3-fold in 11-deoxycortisol at 24 hours in patients with ectopic ACTH; the increase was greater than 3-fold in all but one of the patients with Cushing's disease. Failure to respond to either dexamethasone or metyrapone was found in only one of the patients with Cushing's disease (Patient 16); in the ectopic group, all patients except Patient D failed to respond to either test. It is concluded that patients presenting with clinically obvious Cushing's syndrome along with measurable plasma ACTH can be reliably divided by conventional tests into those that are driven from the pituitary and those driven by ectopic ACTH.

Plasma concentration of atrial natriuretic hormone during endogenous glucocorticoid hypercorticism

In vitro studies have shown that glucocorticoids may increase atrial natriuretic-hormone (ANH) synthesis and/or release. This action of glucocorticoids has also been suggested in vivo in patients with Cushing's syndrome. However, in this circumstance, plasma AH elevation might be due to humoral disturbances associated with cortisol overproduction. We studied 16 patients with endogenous hypercorticism and 11 of them after successful treatment. Plasma levels of ANH, plasma renin activity (PRA), aldosterone, desoxycorticosterone (DOC), angiotensin II (AII), cortisol, osmolarity, sodium and potassium, urinary free cortisol (UFC), and blood pressure were measured. Before treatment the mean plasma ANH concentration in patients with Cushing's syndrome was significantly higher than in controls (11.3 +/- 2.6 vs. 4.9 +/- 2.3 pmol/l; p less than 0.001). ANH was correlated with cortisol and UFC (r = 0.715, r = 0.700; p less than 0.05). There was no significant correlation between plasma ANH, PRA, aldosterone, DOC, AII, osmolarity, sodium or blood pressure. After recovery, ANH concentration decreased in all patients and was not different from that of normal subjects (4.9 +/- 2.3 vs. 4.3 +/- 2.6 pmol/l). These results suggest that in Cushing's syndrome, ANH secretion is mainly dependent on the severity of hypercortisolism and independent of the other associated disturbances that we studied.

Inhibition of human adrenal androgen secretion by ketoconazole

The effect of ketoconazole on adrenal androgen secretion was examined in 15 patients with elevated serum androgens. In a dose of 600 mg per day orally ketoconazole inhibited the biosynthesis of all measured androgens. The mean reduction in serum levels of dehydroepiandrosterone sulfate was 32%, of dehydroepiandrosterone 54%, of androstenedione 52%, and of testosterone 43%; mean serum levels of cortisol only fell by 19%. The reduction in serum androgen levels was first significant 24 h after beginning of treatment and persisted as long as the drug was administered. We conclude that ketoconazole inhibits adrenal androgen biosynthesis more pronouncedly than cortisol biosynthesis more pronouncedly than cortisol biosynthesis. This might be of clinical benefit in the treatment of hirsutism and other states of androgen hypersecretion.

The ovine corticotropin-releasing hormone (CRH) stimulation test is superior to the human CRH stimulation test for the diagnosis of Cushing's disease

The ovine CRH (oCRH) stimulation test is useful in distinguishing Cushing's disease from the syndrome of ectopic ACTH secretion. Most patients with Cushing's disease have increased plasma ACTH and cortisol responses to oCRH, while patients with the ectopic ACTH syndrome do not. We predicted that the homologous hormone human CRH (hCRH) might be an equally useful diagnostic agent, with the theoretic advantage of being less immunogenic. This study compared the responses to hCRH and oCRH (1 microgram/kg, iv) in 15 patients with Cushing's disease. Plasma ACTH and cortisol levels increased in most patients during the first hour after administration of either hCRH or oCRH. However, the peak and time-integrated hormonal responses to hCRH were smaller than the responses to oCRH. All but 1 patient had an ACTH and/or cortisol response to oCRH that exceeded 4 times the intraassay coefficient of variation. Three patients had neither an ACTH nor a cortisol response to hCRH by the same criterion. Thus, when administered at equivalent doses, hCRH is a less effective stimulus of ACTH and cortisol secretion in patients with Cushing's disease. Based upon the observation that the oCRH stimulation test has greater sensitivity than the hCRH stimulation test for the diagnosis of Cushing's disease, we conclude that oCRH is the preferred analog to use for CRH testing in patients with Cushing's syndrome.

Ectopic adrenocorticotropic hormone syndrome: localization studies in 28 patients

A variety of imaging procedures were performed in 28 patients with ectopic adrenocorticotropic hormone (ACTH) syndrome in an attempt to localize the ACTH-producing tumor. Diagnosis was made on the basis of removal of an ACTH-producing tumor or biopsy of metastases in the 19 patients with a proved source and the absence of ACTH gradients in bilateral samples of the inferior petrosal sinuses in the nine patients in whom an ACTH-secreting tumor had not been localized. Eleven bronchial carcinoids, two thymic carcinoids, three pheochromocytomas, and three islet-cell tumors constituted the proved sources. The condition has been cured in eight patients, six are alive with residual tumor, and five have died. Of the nine patients with undetected sites of ACTH production, one has died of pneumocystis pneumonia and eight are being treated medically or with bilateral adrenalectomy. Computed tomography (CT) of the chest and abdomen was the most helpful study in the detection of these tumors. Selective arteriography (bronchial and visceral), systemic and portal venous sampling, and iodine-131 meta-iodobenzylguanidine scintigraphy failed to demonstrate tumors when findings at CT were negative. Bronchial carcinoids constituted most of the ACTH-secreting tumors in this study (58%) and in a review of four large series (47%). To assure early detection of these potentially malignant tumors, pulmonary CT should be performed every 6 months, even after hypercortisolism has been medically or surgically controlled.

Cushing's syndrome due to ACTH-production of an ovarian carcinoid

The case of a 56-year old woman with severe Cushing's syndrome due to ovarian ACTH-production is described. Both clinical picture and biochemical pattern were consistent with the ectopic ACTH syndrome. ACTH was found by specific immunohistochemical staining in a carcinoid tumor of the patient's right ovary. In contrast, pituitary cells exhibited immunoreactive ACTH to only a minimum extent.

Comparative assessment of ACTH and lipotropin plasma levels in the diagnosis and follow-up of patients with Cushing's syndrome: a study of 210 cases

PURPOSE

A series of 210 patients with Cushing's syndrome was evaluated at a single center to assess the relative values of adrenocorticotropic hormone (ACTH) and lipotropin (LPH) plasma levels in the etiologic diagnosis of Cushing's syndrome and in the follow-up of treated Cushing's diseases.

PATIENTS AND METHODS

These patients included 149 patients with Cushing's diseases, 20 with adrenal tumors, and 41 with ectopic ACTH/LPH syndromes. Hormone levels were measured before therapy and during the follow-up of treated Cushing's diseases.

RESULTS

ACTH and LPH plasma levels were moderately elevated in Cushing's diseases, low or undetectable in adrenal tumors, and highly elevated in ectopic ACTH/LPH syndromes, but the overlap between the three etiologic groups was less for LPH than for ACTH. LPH appeared to be as sensitive as ACTH in evaluating the outcome of trans-sphenoidal surgery and in detecting the occurrence of Nelson's syndrome after bilateral adrenalectomy.

CONCLUSION

Therefore, plasma LPH determinations provide a better index than ACTH measurements, probably for technical reasons as well as because of the greater stability of LPH in blood.

Pancreatic insuloma causing Cushing's syndrome

The advent of new diagnostic procedures such as petrosal venous sampling and CRF testing has improved the possibilities of precise location of the site of hormonal overproduction in Cushing's syndrome. We report on a case of ectopic ACTH-dependent Cushing's syndrome in which the use of such techniques helped to locate the tumor. A 45-year-old woman with definite ACTH-dependent Cushing's syndrome was referred to our clinic for evaluation. ACTH, cortisol and urinary 17OHCS failed to suppress on high dose dexamethasone oral administration. Computerized tomography showed bilateral adrenal hyperplasia and an empty sella turcica. ACTH and cortisol did not increase after CRF administration. Staged caval system catheterism via both femoral veins up to the inferior petrosal sinuses, including after CRF administration, demonstrated no ACTH gradient between staged samples and simultaneous peripheral venous blood. This suggested a tumor drained by the portal system. An abdominal ultrasonography demonstrated a pancreatic mass, that was surgically excised and appeared as a benign islet cell tumor. Portal vein ACTH promptly decreased after tumor excision and postoperative peripheral cortisol and ACTH were normal. On immunostaining the tumor cells proved to be positive for ACTH.

A new immunoradiometric assay for corticotropin evaluated in normal subjects and patients with Cushing's syndrome

We evaluated a new, commercially available two-site immunoradiometric assay (IRMA) for corticotropin (ACTH) in human plasma. The precision and detection limit were an improvement over radioimmunoassay (RIA). Addition of ACTH 1-24 or ACTH 18-39 to plasma containing ACTH 1-39 resulted in a decrease in measured ACTH. Results by both IRMA and RIA are reported and compared for normal subjects, patients with Cushing's disease, and patients with ectopic ACTH. Effects of administering dexamethasone, metyrapone, ACTH 1-24, and corticoliberin were evaluated. The present assay is more sensitive, specific, and reproducible than RIA. The presence of fragments of ACTH or "big" ACTH that are reactive in RIA may lead to artifactually low ACTH concentrations by IRMA. Therefore, RIA may still be necessary for differential diagnosis of ectopic ACTH syndromes. However, the IRMA is an improvement for evaluating pituitary--adrenal function in patients with low concentrations of ACTH in plasma.

Two-site immunoradiometric assay for adrenocorticotrophin: a cautionary study about the reactivity to its precursor molecules

The specificity of a "two-site" immunoradiometric assay (IRMA) has been reevaluated by examining its ability to detect heterogeneous adrenocorticotrophin-like immunoreactivity (ACTH-LI) separated by gel column chromatography. Plasma samples from patients with Addison's disease, Nelson's syndrome and ectopic ACTH syndrome and tissue extract of human anterior pituitary were subjected to ACTH-IRMA and the levels of ACTH-LI were compared with those measured by conventional ACTH-radioimmunoassay (RIA). The level of ACTH-LI measured by IRMA was considerably lower than that measured by RIA in the plasma of a case of ectopic ACTH syndrome and the ACTH-LI did not show a dilution curve parallel with that of the standard. Gel exclusion chromatography revealed that the plasma contained a relatively large quantity of "big ACTH" which was found to be poorly detected by the IRMA. In the plasma of Addison's disease or the extract of pituitary gland in which "big ACTH" constituted a small portion, whole ACTH-LI was apparently diluted in parallel with the ACTH standard, although the "big ACTH" also did not show full parallelism with the ACTH standard in the IRMA. These data suggest that "big ACTH" derived not only from an ectopic ACTH-producing tumour but also from a normal human pituitary gland cannot be detected as well as authentic ACTH by the ACTH-IRMA system. Therefore, samples which contain a relatively large proportion of "big ACTH" in the total ACTH-LI should be carefully evaluated by ACTH-IRMA.

Ectopic ACTH production by a thymic carcinoid tumour

An ACTH-producing thymic carcinoid tumour was diagnosed in a 10-year-old girl, 8 years after bilateral adrenalectomy for Cushing's syndrome. The peptides produced by the tumour were characterised thoroughly. High circulating levels of beta-endorphin and other peptides may have contributed to mood and behaviour disturbances.

Ectopic Cushing's syndrome with periodic hormonogenesis--a case suggesting a pathogenetic mechanism

We report on a case of ectopic Cushing's syndrome due to a thymic carcinoid tumour with periodic hormonogenesis. Periods of hormonal production averaged 27 days. Prior to bilateral adrenalectomy, mean (s.d) values of ACTH and cortisol were 202.1 (50.3) pg/ml and 46 (14.7) micrograms/dl, ACTH rising to 3996 +/- 425 pg/ml (P less than 0.01) and cortisol falling to 6.3 +/- 1.5 micrograms/dl (P less than 0.01) in the immediate postoperative period. During the late postoperative period (2-13 months following surgery) ACTH levels fell to 509.3 (123.8) pg/ml (P less than 0.01), but remaining even higher (P less than 0.01) than before adrenalectomy. The pattern of ACTH in the present case suggests the existence of a negative feedback exerted by the cortisol over tumoral ACTH.