Arginine vasopressin in Cushing's disease

Prolactin correction for adequacy of petrosal sinus cannulation may diminish diagnostic accuracy in Cushing's disease

OBJECTIVE

Petrosal venous prolactin concentrations have been promoted to improve the diagnostic accuracy of inferior petrosal sinus sampling (IPSS), beyond that achieved with ACTH measurement alone, in diagnosing a pituitary ACTH source and determining corticotrophinoma side (L/R). Our objective was to assess the effect of using prolactin to confirm adequacy of petrosal cannulation in a cohort of patients with ACTH-dependent Cushing's syndrome.

DESIGN

Retrospective cohort study.

PATIENTS

Thirteen patients with clinical and biochemical Cushing's syndrome who underwent IPSS.

MEASUREMENTS

Serum prolactin and ACTH in peripheral and inferior petrosal sinus blood before and after corticotrophin-releasing hormone (CRH) injection.

RESULTS

Thirteen consecutive patients were diagnosed with Cushing's disease using uncorrected ACTH ratios. The side of PRL excess was the same as the side of ACTH excess in all cases. Use of various published prolactin-related equations suggested that the ACTH non-dominant side was not cannulated in four, six or seven patients depending on the equation used. The equations generally decreased the central-to-peripheral gradient on the uncorrected ACTH dominant side, increased the central-to-peripheral gradient on the contralateral side and diminished or even reversed the ACTH intersinus gradient.

CONCLUSIONS

Consistent co-lateralisation of prolactin and ACTH in IPSS strongly suggests that prolactin cannot act as an independent guide to the diagnosis and lateralisation of Cushing's disease. All patients with Cushing's disease had a prolactin intersinus gradient towards the tumourous side of the pituitary, for likely biological reasons. PRL-corrected ACTH concentrations may threaten the sensitivity and specificity of IPSS in diagnosing Cushing's disease and conceal lateralisation.

Hypothalamus-pituitary-adrenal axis in central diabetes insipidus: ACTH and cortisol responsiveness to CRH administration

A strong relationship has been found between arginine-vasopressin (AVP) and hypothalamus-pituitary-adrenal axis in humans. The aim of the current study was to evaluate baseline and CRH-stimulated ACTH and F levels in patients with central diabetes insipidus (CDI), before and after replacement therapy with desamino-D-AVP (DDAVP). Twenty-five patients with CDI, and 25 sex- and age- and BMI-matched healthy subjects entered the study. A standard CRH test (measurement of plasma ACTH and serum F before and every 15 min for 2 h after the administration of 100 microg of human CRH) was performed in all subjects. In patients with CDI, CRH test were repeated after 1 week of DDAVP at standard doses. At study entry, ACTH and F levels were significantly higher in patients with CDI than in controls either at baseline (ACTH: 45.5+/-4.8 vs 18.5+/-3.3 ng/l, p<0.05; F: 375.1+/-55.7 vs 146.6+/-19.4 microg/l, p<0.05) or after CRH test considered as a peak (ACTH: 90.8+/-14.4 vs 42.5+/-7.4 ng/l, p<0.05; F: 501.6+/-65.7 vs 226.3+/- 25.6 microg/l, p<0.05) and AUC (ACTH: 3997.0+/-571.7 vs 2136.0+/-365.8 ng/l/120 min, p<0.05; F: 31,489.0+/-4299.4 vs 14,854.5+/-1541.5 microg/l/120 min, p<0.05). In patients with CDI, 1 week of replacement with DDAVP brought down ACTH (peak: 56.9+/-9.3 ng/l; AUC: 2390.7+/-480.7 ng/l/120 min) and F (peak: 310.3+/-39.5 microg/l; AUC: 17,555.5+/-2008.7 microg/l/120 min) responses to CRH to normal but did not significantly modify baseline hormone levels (ACTH: 29.6+/-3.6 ng/l; F: 239.0+/-32.3 microg/l). In conclusion, CDI is associated to increased baseline ACTH and F levels and increased responsiveness of ACTH and F to CRH administration. In addition, replacement treatment with DDAVP normalized CRH-induced but not baseline ACTH and F secretion.

Optimal response criteria for the human CRH test in the differential diagnosis of ACTH-dependent Cushing's syndrome

The CRH test is in widespread use for the differential diagnosis of ACTH-dependent Cushing's syndrome (CS). Despite the greater availability worldwide of human-sequence CRH (hCRH), there are no large series reporting the response criteria that best discriminate between Cushing's disease (CD) and the ectopic ACTH syndrome (EC) when using hCRH, rather than ovine-sequence CRH. We have, therefore, analyzed retrospectively the serum cortisol and plasma ACTH responses to hCRH in patients with ACTH-dependent CS, to develop response criteria that best discriminate between CD and EC. One hundred fifteen consecutive patients with proven ACTH-dependent CS were studied: 101 with CD (78 females; mean age, 40 yr; range, 10-73) and 14 with EC (7 females; mean age, 46 yr; range, 32-69). The response to hCRH was also studied in 30 normal volunteers (NVs; mean age, 29 yr; range, 20-44) with no clinical evidence of CS, and the results were compared. Following basal sampling at -15 and 0 min, hCRH (100 microg iv) was administered via an indwelling forearm cannula at 0900 h and serum cortisol and ACTH were measured at 15-min intervals for 2 h. The mean basal, peak, incremental, and percentage change in the serum cortisol and ACTH at all time points, and combination of time points, were calculated and analyzed to establish the best criteria to discriminate between CD and EC, and also between CD and NVs. The mean serum cortisol concentration in samples obtained at 15 and 30 min after CRH increased by at least 14% above the mean basal in 85 of 100 patients with CD, but in none with EC, giving a sensitivity of 85% at a specificity set at 100%. In contrast, the best plasma ACTH response of a rise of 105%, calculated from the maximal rise, gave only 70% sensitivity at 100% specificity. In the NVs, the maximum cortisol at the mean 15+30 min time point was 615 nmol/liter. Using the 15 and 30 min time points as the reference point, 71 of 100 patients with CD had a rise of serum cortisol greater than 14% and also showed an absolute cortisol level more than 615 nmol/liter. Serum cortisol responses to hCRH can be used to suggest the diagnosis of CD in the majority of patients with this condition, but it should only be used in conjunction with other biochemical and imaging modalities in establishing this important diagnosis. The measurement of plasma ACTH was less helpful in making this distinction, although it may have additional value in excluding ACTH-independent causes of CS. Although we believe that bilateral inferior petrosal sinus sampling remains the single most useful test in discriminating CD from EC in patients with ACTH-dependent CS, hCRH offers rapid diagnostic information and is a useful adjunctive test in establishing the presence of a possible ectopic source.

Cushing's disease: a surgical view

The management of adrenocorticotropic hormone (ACTH)-dependent Cushing's disease implies difficulties in the differential diagnosis, in the detection of minute pituitary adenomas, as well as in the radical removal of invasive adenomas. Magnetic resonance imaging (MRI) is unspecific and often negative in minute adenomas of three or less millimeters diameter. The trias of detectable ACTH, suppression of cortisol in the high-dose dexamethasone test, and stimulation in the corticotropin-releasing-hormone (CRH)-test has a high accuracy to prove pituitary dependency. In unclear cases, the use of inferior petrosal sinus sampling (IPSS) or cavernous sinus sampling (CSS) for the exclusion of ectopic ACTH-syndrome is currently advised especially in cases where cranial MRI is negative. The reliability of these methods to localize the mostly lateralized microadenomas is still discussed. Transsphenoidal microsurgical adenomectomy, the accepted primary therapy of Cushing's disease, has been published from experienced pituitary centers with remission rates ranging from 70% to 98% in the last decade. False diagnosis (pseudo-Cushing, ectopic ACTH-syndrome), incorrect adenoma localization by IPSS or CSS, and the rate of minute or non-resectable invasive tumors influence the results. The handling of minute specimen implies problems for surgeon and pathologist. Intraoperative tumor localization was improved by ACTH measurement from the cavernous sinus and the adenoma itself, by cytology, and frozen sections. The histology of the anterior lobe (rate of Crooke's cells) bears information of clinical relevance. Invasive macroadenomas may deserve repeat microsurgery, medical treatment, and radiosurgery.

Cushing’s disease and melancholia

Striking similarities exist in the endocrinology of Cushing's disease and melancholic depression.Laboratory abnormalities, which have been found in both, include raised urinary,plasma and salivary cortisol, non-suppression of cortisol in the dexamethasone suppression test and adrenocorticotrophin (ACTH) hypersecretion. The hypercortisolism can be so severe in melancholic depression that it is difficult to distinguish from Cushing's disease and has been described as a "pseudo-Cushing's" state. Cerebrospinal fluid corticotrophin-releasing hormone (CRH) levels have been found to be lower in patients with Cushing's disease than in depressed subjects. Dynamic endocrine tests may help to distinguish between the two disorders.An exaggerated response to synacthen has been found in both but a reduced ACTH response to CRH occurs in depression, unlike those with Cushing's disease who show ACTH hyper-responsiveness. Other tests, which may help to distinguish between the two disorders,include the dexamethasone-CRH test, the naloxone test, the insulin-induced hypoglycemia test and the desmopressin stimulation test. Similarities in psychiatric symptoms have been recognised for many years. More recently, the physical complications of melancholic depression have been noted. These include osteoporosis, an increased risk of death from cardiovascular disease, hypertension, a redistribution of fat to intra abdominal sites and insulin resistance. Cushing's disease shares these physical complications and we propose that the common underlying factor is excessive plasma glucocorticoids. The increasing recognition of the physical complications and the increased morbidity and mortality in those who suffer from depression underscores the necessity for early detection and treatment of this illness and screening for undetected physical complications.

Overexpression of vasopressin (V3) and corticotrophin-releasing hormone receptor genes in corticotroph tumours

OBJECTIVE

The molecular mechanisms underlying ACTH-secreting tumour formation remain unknown. Transmembrane signalling pathways play an important role in several endocrine disorders including pituitary tumours. To investigate the role of the pituitary vasopressin (V3) receptor (R) in ACTH-secreting tumours we have qualitatively and quantitatively analysed its mRNA.

DESIGN

RT-PCR, denaturing gradient gel electrophoresis and S1 nuclease protection experiments were used to analyse V3 mRNA structure in ACTH-secreting tumours. We also developed a competitive RT-PCR system to compare the levels of expression of POMC, V3 and CRH-R genes. This system used as competitor a single mutant template (termed multi-mutant) containing primers for the three genes flanking an unrelated core sequence allowing multiple quantifications from the same cDNA preparations. We analysed 12 normal pituitaries, 15 corticotroph pituitary adenomas and 6 ACTH-secreting bronchial carcinoids.

RESULTS

The V3 mRNA structure and sequence were found to be identical in normal and tumoural pituitary indicating that the tumoural Vs mRNA codes for a normal receptor. POMC RT-PCR signals in the pituitary tumour group were approximately 7-fold higher than in the normal pituitary group. Similarly, V3 and CRH-R signal were increased in pituitary tumors (mean +/- SEM: 5.87 x 10(-6) +/- 1.73 x 10(-6), and 2.33 x 10(-4) +/- 1.4 x 10(-4), respectively), when compared to normal pituitaries (1.19 x 10(-7) +/- 2.39 x 10(-8), and 1.7 x 10(-6) +/- 4.65 x 10(-7), respectively) suggesting that these two genes are expressed at very high levels in corticotroph tumours. When expressed relative to the corresponding POMC signals, increases in V3 and CRH-R signals reached 49-fold and 137-fold, respectively, in pituitary tumours. In ACTH-secreting bronchial carcinoids V3 gene expression level was also higher than in normal pituitary, whereas CRH-R signals were detected in only 4 of the 6 tumours with wide variations.

CONCLUSION

Our results show that both vasopressin and CRH receptor genes are overexpressed in ACTH-secreting pituitary tumours. They suggest that overexpression of G protein-coupled receptors may be an additional mechanism through which membrane receptors may play a role in human tumours.

Effect of corticotrophin-releasing hormone on arginine vasopressin and atrial natriuretic factor in patients with Cushing's disease

OBJECTIVE

To evaluate the effect of CRH administration on plasma AVP and ANF concentration in patients with Cushing's disease and healthy subjects.

SUBJECTS

Fifteen patients with Cushing's disease and 15 sex- and age-matched healthy subjects entered the study.

STUDY DESIGN

All subjects were randomly given i.v. 100 micrograms hCRH and placebo (NaCl 0.9%) on two non consecutive days. Blood samples for plasma AVP and ANF assay were taken before and every 15 min for 2 hr after CRH or placebo. Five out of the 15 patients with Cushing's disease underwent a repeat CRH test after surgical cure of the disease.

RESULTS

At baseline evaluation, plasma ANF concentrations were significantly higher in patients with Cushing's disease compared to healthy subjects (15.0 +/- 0.8 vs 10.8 +/- 0.6 pmol/l, P < 0.001) whereas plasma AVP concentrations were similar between the two groups of subjects (8.0 +/- 0.4 vs 6.8 +/- 0.6 pmol/l). CRH administration induced a significant increase in plasma ANF concentrations both in patients with Cushing's disease (24.0 +/- 1.6 pmol/l, P < 0.05) and healthy subjects (29.4 +/- 1.5 pmol/l, P < 0.05). Conversely, a significant increase in plasma AVP concentrations was found only in patients with Cushing's disease (14.7 +/- 1.4 vs 8.0 +/- 0.4 pmol/l, P < 0.05). In addition, patients with Cushing's disease had an increase in ANF levels after CRH significantly lower than that observed in healthy subjects (peak/basal ratio: 1.7 +/- 0.1 vs 3.1 +/- 0.4, P < 0.01). In 5 patients re-tested after disease cure, CRH administration significantly increased plasma ANF levels (26.8 +/- 1.1 vs 10.7 +/- 0.4 pmol/l, P < 0.05) but it did not modify plasma AVP levels (8.4 +/- 0.4 vs 7.3 +/- 0.5 pmol/l). ANF response to CRH in patients cured from Cushing's disease was similar to that recorded in healthy subjects (peak/basal ratio: 2.6 +/- 0.2 vs 3.1 +/- 0.4).

CONCLUSION

CRH stimulates ANF secretion both in patients with Cushing's disease and healthy subjects. Plasma ANF response to CRH is blunted in patients with Cushing's disease compared to patients cured from Cushing's disease and healthy subjects, probably because of hypercortisolism. By contrast, CRH stimulates AVP secretion only in patients with Cushing's disease, but not in patients cured from Cushing's disease and healthy subjects. This phenomenon could be related to the activity of the disease.

The neuroendocrine immunology of rheumatoid arthritis

Rheumatoid arthritis patients have defective neuroendocrine-immune responses to the stress of inflammation, and currently available data shows that this contributes to the pathophysiology of the disease. The advances in neuroendocrine immunology have improved our understanding of the pathophysiological mechanisms involved in RA. These observations raise important therapeutic questions which are certainly worth further investigation as they may open up novel avenues for the management of the disease.

Benzodiazepines attenuate the pituitary-adrenal responses to corticotrophin-releasing hormone in healthy volunteers, but not in patients with Cushing's syndrome

OBJECTIVE

The corticotrophin-releasing hormone (CRH) stimulation test has become established as a powerful tool in differentiating the source of ACTH in patients with Cushing's syndrome. Psychiatric symptoms are common in patients with Cushing's syndrome, and many patients with psychiatric illnesses may show disturbances of function of the pituitary-adrenal axis; both of these groups of patients may be receiving benzodiazepine drugs when presenting for evaluation of their possible endocrine problems. Both animal and human studies suggest that interactions occur between benzodiazepines and the hypothalamo-pituitary-adrenal axis. We have therefore evaluated the effects of a benzodiazepine drug on the pituitary-adrenal response to CRH.

DESIGN

We have investigated the effects of 20 mg oral temazepam or placebo on serum cortisol and plasma ACTH after the administration of 100 micrograms i.v. human CRH in 12 healthy volunteers and in 9 patients with Cushing's syndrome.

RESULTS

Temazepam significantly inhibited the peak serum/plasma levels and area under the curve for circulating cortisol and ACTH in normal subjects after CRH, but there was no such difference after temazepam in patients with Cushing's syndrome.

CONCLUSIONS

Our results have shown that temazepam inhibits the pituitary-adrenal responses to human CRH in normal subjects, but not in those with Cushing's syndrome. We believe that inhibition of endogenous AVP by temazepam is the most likely explanation for our findings in healthy volunteers: the hypercortisolaemia in Cushing's syndrome suppresses the release of both endogenous CRH and AVP in portal blood which then results in abolition of the temazepam induced reduction in the pituitary-adrenal response to exogenous CRH, as seen in our patients. These effects of benzodiazepines should clearly be taken into account in patients using these compounds while undergoing endocrine assessment.

Glucocorticoid responsive ACTH secreting bronchial carcinoid tumours contain high concentrations of glucocorticoid receptors

Cushing's syndrome due to a bronchial ACTH secreting carcinoid tumour may be difficult to distinguish from a pituitary microadenoma (corticotrophinoma) causing Cushing's disease, since in both disorders ACTH secretion may be responsive to glucocorticoids. Why some bronchial carcinoid tumours are responsive is unknown but it could be because of co-secretion of corticotrophin releasing factor (CRF) and/or expression of glucocorticoid receptors. We report two patients with glucocorticoid responsive ACTH secreting bronchial carcinoid tumours, neither of whom produced or responded to CRF. Significant glucocorticoid receptor binding capacity (92 and 102 pmol/g protein), compared with control lung tissue, was found in extracts from both tumours. These findings suggest that corticotrophinoma-like responses to glucocorticoids observed in some ACTH secreting bronchial carcinoids result from expression of glucocorticoid receptors and are not necessarily related to the production of CRF.

Corticotrophin releasing hormone (CRH1-41) stimulates the secretion of adrenocorticotrophin, vasopressin and oxytocin but not adrenocorticotrophin precursors: evidence from petrosal sinus sampling in man

To examine the relationship between corticotrophin releasing hormone (CRH), arginine vasopressin (AVP) and oxytocin (OXT) we have studied the responses of adenohypophyseal and neurohypophyseal hormones to CRH in eight patients (age 26-64 years, six female) with suspected pituitary-dependent Cushing's syndrome during bilateral, simultaneous inferior petrosal sinus catheterization. Blood samples were taken from both petrosal sinuses and a peripheral vein before, and at 5-min intervals for 15 min after, an intravenous injection of 100 micrograms human CRH1-41. CRH increased sinus AVP concentrations in all eight patients and OXT concentrations in four of five patients studied. Although AVP concentrations often increased in both sinuses, the side of maximal AVP rise was termed side(max-AVP). CRH did not affect peripheral or petrosal sinus mean concentrations of LH, FSH, GH or TSH. While there was no change in mean peripheral concentrations of AVP, OXT, ACTH, ACTH precursors or prolactin after CRH, sinus concentrations of OXT, ACTH and prolactin on side(max-AVP) were markedly elevated over contralateral values. CRH did not increase mean sinus concentrations of ACTH precursors. In seven patients with either no radiological abnormality or the pituitary fossa or a small adenoma the mean ACTH precursor/ACTH ratio in blood sampled from all sites was 2.1 +/- 0.16 (mean +/- SEM, n = 50). In a patient with a large, locally invasive tumour the mean ACTH precursor/ACTH molar ratio was 32.1 +/- 1.3 (n = 12; P less than 0.001), suggesting that alterations in this molar ratio may reflect the biological properties of the tumour. The source of CRH-stimulatable AVP and OXT remains uncertain.(ABSTRACT TRUNCATED AT 250 WORDS)