Corticotropin-releasing factor-like activity in ACTH producing tumors

Ectopic cushing's syndrome due to corticotropin releasing hormone

Cushing's syndrome (CS) secondary to corticotropin releasing hormone (CRH) producing tumors is rare. In this paper we present an Iranian patient who was admitted to our hospital with classic signs and symptoms of CS. Laboratory evaluation revealed high serum and urine cortisol which could not be suppressed with dexamethasone. Abdominal CT scan revealed a mass in abdominal cavity. A percutaneous needle biopsy was performed and histopathologic evaluation revealed that the mass was a neuroendocrine tumor. A multi-disciplinary approach including resection of the mass, bilateral adrenalectomy somatostatin analogue and chemotherapy was applied for management of the disease. Extensive review of English literature focusing on the topic from 1971 to 2018 revealed that there have been only 75 similar cases. Clinical, laboratory, imaging, histopathologic characteristics and managements of these patients will also be discussed in this paper.

ACTH-Secreting Neuroendocrine Carcinoma of the Cecum: Case Report and Review of the Literature

BACKGROUND

Approximately 30% of neuroendocrine tumors (NETs) present with secretory syndromes or develop one during the course of the disease. Cushing syndrome caused by a gastrointestinal tract NET is rare, with limited published information. We describe a patient with florid Cushing syndrome due to ectopic adrenocorticotropic hormone (ACTH) from a NET of colonic origin. A literature review was conducted to describe the spectrum of this clinical and pathologic entity as reported in the scientific literature.

PATIENT AND METHODS

Next-generation sequencing and microsatellite instability testing was carried out on the tumor from our case. A preliminary PubMed search was conducted using the following terms under the publication type "Case Reports": "Cushing" AND "colon," "neuroendocrine" AND "colon" and "neuroendocrine AND Cushing AND "colon." A manual search was performed to review all references for inclusion and relevant clinical, biochemical and pathologic data was abstracted.

RESULTS

Mutations in BRAF V600E and TP53 were detected in our case. We retrieved 18 previously reported cases of Cushing syndrome associated with a NET of colonic origin, none of which had next-generation sequencing performed. Median age at diagnosis was 54.5 years (range, 24-74 years), with equal gender distribution. ACTH was detected by immunohistochemistry in the primary tumor and/or metastatic lesion in 61.5%. Review of the reports suggested that ectopic ACTH secretion from a colonic tumor might be more common in mixed glandular and NETs, including mixed adenocarcinoma-neuroendocrine carcinoma. Among studies reporting outcomes, the unadjusted mortality rate was 77.7%, with median overall survival from presentation of 63 days (range, 17-380 days).

CONCLUSION

Cushing syndrome associated with ectopic ACTH from tumors of colonic origin is a rare phenomenon with poor outcomes and can be associated with pure NETs, adenocarcinomas, and mixed-phenotype tumors, including mixed adenocarcinoma-neuroendocrine carcinoma.

Corticotropin-releasing hormone production by a small cell carcinoma in a patient with ACTH-dependent Cushing's syndrome

We describe a patient with Cushing's syndrome and metastatic small cell lung cancer. The plasma ACTH concentrations were markedly elevated (91.6 pmol/L), and the AM cortisol did not suppress by > 50% overnight after administration of 8 mg dexamethasone, both consistent with the ectopic ACTH syndrome. Immunohistochemical studies of a single metastatic tumor specimen, however, demonstrated an absence of ACTH and yet an abundance of corticotropin-releasing hormone (CRH). In addition, radioimmunoassay of the patient's plasma demonstrated persistently elevated CRH concentrations. The majority of the plasma CRH immunoreactivity exhibited the same chromatographic mobility as synthetic r/h CRH (1-41) on HPLC. Failure to evaluate the tumor tissue for the presence of ACTH and/or CRH would have led to the erroneous conclusion that this patient's Cushing's syndrome resulted from paraneoplastic ACTH production. We conclude that immunoassay of plasma for both ACTH and CRH and, perhaps, immunostaining of tumor samples are required to distinguish between the ectopic ACTH and CRH syndromes.

Limited clinical usefulness of plasma corticotropin-releasing hormone, adrenocorticotropin and beta-endorphin measurements as markers of lung cancer

We measured plasma corticotropin-releasing hormone (CRH), ACTH, beta-endorphin (beta-EP), and cortisol levels as possible tumor markers in a sequence of 103, randomly selected, patients with lung cancer but without the ectopic Cushing's syndrome and in 72 age- and sex-matched controls. Plasma CRH levels of cancer patients were similar to those of controls both in patients sampled in the morning or in the afternoon. On the other hand, plasma ACTH levels of cancer patients were significantly higher than control patients both in the morning and in the afternoon and showed a preserved circadian rhythm. However, about 35% of cancer patients sampled in the morning and about 60% of those sampled in the afternoon had ACTH levels within the 95% confidence interval (CI) of controls. Also plasma beta-EP levels were more elevated in cancer patients than controls in the morning but about 33% of them and about 80% of those sampled in the afternoon had beta-EP levels within the 95% CI of controls. Despite the higher plasma ACTH levels, cancer patients had cortisol plasma levels similar to controls with preserved circadian rhythm. In conclusion, although mean plasma ACTH and beta-EP were higher in patients affected by lung cancer, their measurements, as well as those of CRH, have practically no diagnostic value. Perhaps measurement of ACTH levels in the bronchial lavage may be more helpful.

Diagnosis of lung carcinoid with cutaneous hyperpigmentation eight years after bilateral adrenalectomy

A 26-yr-old male was submitted to bilateral adrenalectomy in 1977 for Cushing's syndrome. Some months later he developed intense skin hyperpigmentation together with increased ACTH levels (149 to 4000 ng/l). The sellar region was always normal in X-ray studies. In April 1985, when the patient complained of chest pain, a chest x-ray showed a polycyclic mass in the upper left lobe of the lung. ACTH ranged from 20,000 to 100,000 ng/l, with no response to CRF or cyproheptadine administration. Urinary 5-OH-indolacetic acid was negative. Thoracotomy was performed in July 1985 with resection of two intrapulmonary masses. Histologic study demonstrated a carcinoid tumor, with positive neuron-specific enolase and ACTH immunochemical stain. ACTH concentration in tumoral tissue was 91 pg/g tissue. After surgery ACTH fell dramatically to 37 ng/l, and has remained at this level since then, associated with resolution of the skin hyperpigmentation.

ACTH and CRF-producing bronchial carcinoid associated with Cushing's syndrome

A young female patient, with clinical and biochemical manifestations of severe hypercorticism and with the presence of a pituitary adenoma shown by computerized tomography, was thought to have Cushing's syndrome of hypophysial origin. However, the surgically-removed pituitary adenoma contained no ACTH, by immunocytology, and hypercorticism persisted after transsphenoidal adenomectomy. The patient died and autopsy demonstrated an ACTH and corticotrophin releasing factor (CRF)-containing bronchial carcinoid. It can be concluded that bronchial carcinoids can produce ACTH and CRF and can mimic the clinical and biochemical manifestations of pituitary Cushing's syndrome. Thus, the localization of the primary site of hypercorticism can be extremely difficult in patients who have an insidious, occult extrapituitary tumour. Further work is required to establish whether CRF plays a role in the causation of Cushing's syndrome and whether the simultaneous secretion of this peptide can modify the clinical and biochemical manifestations of the ectopic ACTH syndrome.

Demonstration of corticotropin-releasing factor binding sites on human and rat erythrocyte membranes and their modulation by chronic ethanol treatment in rats

In a previous study we reported the presence of specific corticotropin-releasing factor (CRF) binding sites in peripheral tissues of the rat (Endocrinology, 116, 2152, 1985). Using 125I-labeled rat or human CRF, specific CRF binding sites were identified on rat and human erythrocytes, but not on lymphocytes or platelets. Furthermore, identical CRF binding was observed in the presence of intact erythrocytes or lysed erythrocyte membranes. Maximal binding of 125I-CRF occurred within 25 min at 4 degrees C and was saturable. Scatchard analysis of CRF binding to erythrocyte membranes revealed the existence of a single class of binding site. Chronic exposure of rats to ethanol vapor, known to lower specific CRF binding to pituitary tissue by 35%, also decreased 125I-rat CRF binding to erythrocyte membranes by approximately 45%, which was due to a decrease in the number of CRF binding sites. The parallel decrease of CRF binding to rat-erythrocyte and pituitary membranes following chronic ethanol treatment suggests that CRF binding to erythrocyte and pituitary membranes is modulated in a similar direction, which further suggests that the determination of CRF binding to erythrocytes may provide an important clinical tool to indirectly assess CRF-receptor levels in the pituitary gland and thereby enhance our understanding of ethanol-induced disorders of the hypothalamic-pituitary-adrenal axis in patients.

Demonstration that corticotropin-releasing factor binding to rat peripheral tissues is modulated by glucocorticoid treatment in vivo and in vitro

In a recent study we reported the presence of specific binding sites for corticotropin-releasing factor (CRF) in peripheral tissues of the rat (Endocrinology, 116, 2151, 1985). The objective of this study was to determine if CRF binding to peripheral tissues was modified following adrenalectomy and glucocorticoid replacement therapy. Adult male rats were adrenalectomized and CRF binding to liver, spleen and testicular membranes was determined at 5, 7 or 14 days following adrenalectomy. An additional group of adrenalectomized rats received subcutaneous injections of dexamethasone (75 micrograms/day) for 14 days. Adrenalectomy of rats for 14 days increased CRF binding to liver, kidney, testis, spleen and ventral prostate by approximately 65%-125% above sham-control values. CRF binding to membrane preparations obtained from the pancreas of sham-operated rats was undetectable; however, adrenalectomy produced detectable CRF binding in this tissue. Adrenalectomy produced a time-related increase in CRF binding to ventral prostate, spleen and liver tissue. Administration of dexamethasone to adrenalectomized animals prevented increased CRF binding to peripheral tissues observed following adrenalectomy alone. In vitro dexamethasone treatment of prostatic or hepatic homogenates from adrenalectomized rats resulted in a dose-related decrease in CRF binding activity. However, similar in vitro treatment of prostatic or hepatic homogenate with progesterone exhibited no significant effects on CRF binding. Our results suggest that glucocorticoids may be a regulator of peripheral CRF receptors.

Corticotropin-releasing factor (CRF)--a review

Corticotropin-releasing factor (CRF), a 41 amino acid polypeptide, has been isolated from ovine hypothalamic extracts, sequenced, and synthesized. It has a high potency for stimulating the secretion of corticotropin-like and beta-endorphin-like immunoactive substances in vitro and in vivo in laboratory animals and humans. The high concentration of CRF-like immunoactivity in hypophyseal portal plasma supports the hypothesis that CRF is the physiological hypothalamic factor. Human and rat CRF (rCRF) also have been purified and synthesized. They have an 83% sequence homology with ovine CRF (oCRF). oCRF-like activity has been found in human hypothalamus, pituitary stalk, posterior pituitary, thalamus, cerebral cortex, cerebellum, pons, medulla oblongata, spinal cord and in the adrenal, lung, liver, stomach, duodenum and pancreas. oCRF-like activity also has been found in the human placenta and in tissues producing ectopic ACTH. The action of CRF can be potentiated by vasopressin, oxytocin, epinephrine, norepinephrine, VIP, and angiotensin II. Intracerebroventricular administration of CRF in the rat produces prolonged elevations of plasma epinephrine, norepinephrine, glucose and glucagon; elevates mean arterial pressure and heart rate; increases motor activity and exploration in familiar surroundings and oxygen consumption; and decreases feeding and sexual behavior. Testing with CRF has enabled the separation of patients with hypothalamic and pituitary adrenal insufficiency. The CRF stimulation test has been useful in distinguishing pituitary from ectopic causes of Cushing's disease. The distribution of CRF within and beyond the hypothalamus provides an anatomical context for the observation that CRF can simultaneously activate and coordinate metabolic, circulatory and behavioral responses that are adaptative in 'stressful' situations. CRF not only stimulates the pituitary-adrenal axis in man, but it also influences several aspects of CNS function which may be of relevance to psychiatric illnesses.

Cushing's syndrome

Cushing's syndrome remains one of the most challenging problems in clinical endocrinology. Cushing's disease is caused in the majority of cases by basophil pituitary microadenomas which may be successfully treated by trans-sphenoidal hypophysectomy. Treatment with metyrapone or o,p'-DDD can always induce a clinical remission but not a cure, and neurotransmitter therapy may be effective in a minority of cases. Pituitary irradiation cures about half of cases in the long-term and may be used for surgical failures. Tumours producing ectopic ACTH are frequently benign, small and occult and may produce a syndrome clinically indistinguishable from Cushing's disease. Biochemical investigations cannot absolutely distinguish pituitary from ectopic sources of ACTH and therefore body CT scanning and percatheter venous sampling are essential diagnostic investigations. Tumour localization may result in resection and complete cure, although even small tumours may have a malignant potential. Adrenal tumours are readily diagnosed by plasma ACTH measurement and adrenal CT scanning. Adrenal adenomas are cured by adrenalectomy. Carcinomas may be treated by a combination of adrenalectomy, radiotherapy and o,p'-DDD, but long-term prognosis is poor.

Presence of corticotropin-releasing factor-like immunoreactivity in human tumors

Corticotropin-releasing factor (CRF)-like immunoreactivity was measured by radioimmunoassay in human organs and tumors associated with and without ectopic adrenocorticotropic hormone (ACTH) syndrome. It was found to be distributed widely in the stomach, pancreas, adrenal gland, and various tumors (e.g., medullary thyroid carcinoma, small cell carcinoma of the lung, pheochromocytoma, and adenocarcinoma of the gastrointestinal tract and pancreas) in a concentration less than one tenth of that of the hypothalamus. Dilution curves of CRF-like immunoreactivity in tissue extracts paralleled that of synthetic rat (human) CRF. Sephadex G-50 gel filtration showed that a major CRF-like immunoreactivity in tissue extracts coeluted with synthetic rat (human) CRF. Results suggest that a material(s) closely related immunologically to CRF is present widely in normal and tumor tissues outside of the central nervous system.

Pituitary ACTH dependent Cushing's syndrome due to ectopic production of a bombesin-like peptide by a medullary carcinoma of the thyroid

A 41-year-old man presented with Cushing's syndrome and the biochemical features of ectopic ACTH production. Investigation revealed mediastinal metastases from a medullary carcinoma of the thyroid. The peripheral plasma contained grossly elevated levels of bombesin-like immunoreactivity (irBombesin) as well as calcitonin; blood sampling via a venous catheter confirmed a gradient of irBombesin, but not of ACTH, in the mediastinal vein draining the tumour. On extraction the tumour contained a bombesin-like peptide, but not vasopressin or corticotrophin releasing factor and only very low levels of ACTH; immunohistochemical studies showed positive immunostaining for bombesin and calcitonin but none for ACTH or CRF. No ACTH was released from dispersed tumour cells in vitro. However an extract of the tumour stimulated ACTH release in vitro from perifused dispersed rat anterior pituitary cells. This is the first reported case of Cushing's syndrome due to ectopic production of a bombesin-like peptide, causing excessive pituitary ACTH secretion.

Ectopic secretion of corticotropin-releasing factor as a cause of Cushing's syndrome. A clinical, morphologic, and biochemical study

Corticotropin-releasing factor, a hypophyseo-tropic hormone that stimulates adrenocorticotropic hormone (ACTH) secretion, has recently been isolated, characterized, and synthesized in the sheep and rat. We report on a patient with metastatic carcinoma of the prostate presenting with anterior and posterior pituitary hormone deficiency together with ACTH-dependent Cushing's syndrome. At postmortem examination, large areas of the median eminence and pituitary stalk were replaced by tumor, but the corticotrophs were markedly hyperplastic. Immunostaining of tumor cells was positive for corticotropin-releasing factor and was negative for ACTH and a wide range of other hormones. Radioimmunoassay and bioassays showed that tumor extracts and further purified fractions were active in corticotropin-releasing factor, and the tumor material coeluted with corticotropin-releasing factor on high-pressure liquid chromatography. These studies demonstrate that ectopic secretion of corticotropin-releasing factor is a cause of Cushing's syndrome in human beings. The features of this syndrome include hypercortisolism, pituitary corticotroph hyperplasia, elevation of circulating ACTH levels, and failure to suppress the pituitary-adrenal axis with exogenous glucocorticoids.

Corticotropin-releasing factor (CRF)-like immunoreactivity in the gastro-entero-pancreatic endocrine system

CRF has been detected in the endocrine pancreas by immunocytochemistry with an antiserum that recognizes mainly the C-terminal portion of CRF-41. CRF-containing cells have been shown to be present in the pancreas of representative species of fishes, amphibians, reptiles, birds, and mammals including man. Light and electron microscopic observations indicate that the CRF-containing cells in the endocrine pancreas are similar to glucagon (A) cells both in their morphology and distribution. Individual CRF-containing cells are also found scattered in the exocrine pancreas in all species studied. In addition, CRF-containing cells have been identified in the human, monkey, cat, and rat stomach and small intestine. Recent reports also indicate that CRF-like immunoreactivity is present in the circulating blood, the adrenal medulla, and the placenta. Finally, several peripheral (pancreas, stomach, colon, lung and thyroid) tumors which produced corticotropin-releasing substances have been described by others. Although the peripheral actions of CRF are not yet known, these observations indicate that it is widely distributed in peripheral tissues and it may also represent a new tumor marker.

Acromegaly due to production of a growth hormone releasing factor by a bronchial carcinoid tumor

We have studied growth hormone production in a patient with a bronchial carcinoid and acromegaly. The absence of growth hormone from the carcinoid tumour was demonstrated by extraction, cell culture and immunoperosidase techniques. Using a linked perfusion culture system, effluent from the bronchial carcinoid tumour culture stimulated a rapid release of growth hormone from a rat pituitary monolayer. This is the first time evidence of growth hormone releasing activity by a bronchial carcinoid has been demonstrated in a production.