[Paraneoplastic endocrine syndromes]

Among the most interesting manifestations of neoplasms is the production of functional peptides and hormones that may induce unique clinical syndromes. It has become obvious in the last decades that a wide range of endocrine tumors secrete hormones not normally associated with the tissue in which the neoplasm arises. The resultant syndromes, some of which resemble other endocrine entities, can be the first clinical manifestation of malignant disease or a harbinger of cancer recurrence. The development of these disorders does not necessarily correlate with cancer stage or unfavorable prognosis. Early recognition of paraneoplastic endocrine syndromes is clinically important as it might lead to the detection of underlying malignancy and might prevent delay in treatment. Because paraneoplastic endocrine syndromes often cause considerable morbidity and mortality, effective treatment can improve patient quality and length of life. The aim of this study was to review the most common and the most specific paraneoplastic syndromes associated with the presence of ectopic hormone production. We emphasize the importance of considering the ectopic hormone production in the differential diagnosis of various endocrine entities.

Recurrent solitary fibrous tumor of the pleura with malignant transformation and non-islet cell tumor-induced hypoglycemia due to paraneoplastic overexpression and secretion of high-molecular-weight insulin-like growth factor II

A 41-year-old man was diagnosed with a solitary fibrous tumor (SFT) of the pleura in the posterior mediastinum. Despite two surgeries for excision, the SFT recurred and progressed with direct invasion of the chest wall and bone metastases. He was hospitalized because of cerebral infarction and presented with recurrent severe hypoglycemia fourteen years later. High-molecular-weight (HMW) insulin-like growth factor II (IGF-II) was identified in the serum and tumor using Western blotting and immunohistochemistry. These findings suggested that the cause of the recurrent severe hypoglycemia was SFT production of HMW IGF-II, a mediator of non-islet cell tumor-induced hypoglycemia (NICTH).

Immunological function of thymoma and pathogenesis of paraneoplastic myasthenia gravis

Thymoma and thymic carcinoma are the representative tumors arising from the thymic epithelium. Thymoma is well known for association with autoimmune diseases including myasthenia gravis, suggesting its biological activity. Herein, recent progress in research of thymoma is reviewed with reference to its immunological function. Myasthenia gravis is frequently associated with WHO type B1 and B2 thymomas. These types of thymomas hold a significant number of CD4(+)CD8(+) double-positive T cells, and at the same time, the neoplastic epithelial cells express HLA-DR molecules at a slightly reduced level compared with the normal thymus. The impaired expression of HLA-DR molecules in neoplastic epithelial cells of thymomas possibly affects positive selection of CD4(+)CD8(-) single-positive T cells and may result in alteration of its repertoire. The function of thymoma neoplastic cells as the cortical epithelium of the thymus and the morphological resemblance of thymomas to the cortex suggest that thymoma is of cortical epithelial origin; this might imply that thymoma lacks the functional medulla where professional antigen-presenting cells are engaged in negative selection. These findings suggest that thymoma generates autoreactive T cells causing autoimmunity. Further investigation on immunological function of thymoma is supposed to elucidate the pathogenesis of thymoma-related autoimmunity and the high affinity of thymoma with myasthenia gravis. In addition, studying the biology of thymoma is also expected to contribute to further understanding of T-cell development and immunological tolerance in the human, because thymoma can be considered an acquired thymus.

Ectopic adrenocorticotropic hormone-syndrome in medullary carcinoma of the thyroid: a retrospective analysis and review of the literature

Cushing's syndrome (CS) in medullary thyroid carcinoma (MTC) is rare. Only 50 cases have been reported. We report 10 cases of MTC with ectopic adrenocorticotropic hormone (ACTH)-dependent syndrome (EAS), analyzed retrospectively. Among 1640 patients with MTC, 13 developed EAS (0.7%). In 10 patients CS could unequivoqually be related to MTC (0.6%). CS was always clinically obvious. It revealed MTC in 3 cases and followed diagnosis by an average of 34.5 months in the others. Metastases were often present at diagnosis. Immunohistochemistry with ACTH antibodies was positive in one case. Diagnosis of ectopic CS was established according to clinical and biologic features, and absence of corticotropic adenoma as well as parallel evolution between tumor and CS. Therapy was medical and surgical: anticortisolic drugs alone or in association with somatostatin analogue, somatostatin analogue alone, and bilateral adrenalectomy. Eight patients died within 2 to 30 months, 4 of hypercortisolism complications (3 peritonitis and 1 hypokalaemia), 4 of MTC progression. EAS is a rare complication of MTC. The prognosis is poor because of frequency of metastasis at diagnosis. Persistent hypercortisolism can, by itself, lead to death, and has to be treated specifically.

Adrenomedullin and endocrine disorders

Adrenomedullin (AM) is a recently discovered potent vasodilatory peptide, originally isolated in extracts of human pheochromocytoma, with activities including maintenance of cardiovascular and renal homeostasis through vasodilatation, diuresis and natriuresis. Human AM consists of 52 amino acids with a 6-member ring structure linked by a disulfide bond and amidated COOH terminal, which belongs to calcitonin gene-related peptide (CGRP) and amylin. The main sites of AM production are the lungs, vascular tissues (both endothelial and smooth muscle cells), heart, kidney, adrenal glands, pancreatic islets, placenta, anterior pituitary gland and gastrointestinal neuroendocrine system. Intravenous injection of AM increases blood flow predominantly in the tissues with the highest AM expression, suggesting that AM functions primarily as a paracrine/autocrine hormone, but it is also important as circulating hormone. The objective of this review is to analyze the evidence that AM may play a role in some endocrine disorders.

EPO-producing gastric carcinoma in a hemodialysis patient

A case of erythrocytosis caused by gastric cancer that produced erythropoietin is described. To the authors' knowledge, no case of erythropoietin-producing gastric cancer has been reported until now. A 73-year-old man with a 4-year history of maintenance hemodialysis for diabetic nephropathy required phlebotomy. Serum erythropoietin level was 181 mU/mL (181 IU/L). Gastroscopy results showed rough mucosa with hemorrhaging caused by gastric cancer. The patient underwent distal gastrectomy, and serum erythropoietin level decreased to 27.1 mU/mL (27.1 IU/L) by postoperative day 8. Existence of erythropoietin in the tumor tissue was confirmed immunohistochemically. The presence of severe acquired cystic disease of the kidney, renal cell carcinoma, and other malignant tumors should be investigated in hemodialysis patients displaying erythrocytosis.

Endocrine paraneoplastic syndromes in lung cancer

Lung tumors are capable of synthesizing and secreting peptide proteins (hormones) that lead to a variety of endocrine paraneoplastic syndromes. Knowledge about the clinical manifestations, pathophysiology, and treatment of these syndromes has evolved over time. This article provides an up-to-date overview of this knowledge.

[Disordered hormone regulation in gynecomastia]

Gynecomastia develops when there is an increase in the ratio of estrogen to androgens. Whereas mild forms of gynecomastia are frequently encountered in the male population, any breast enlargement that is prominent, painful, progressive or of recent onset always requires a careful evaluation, as it may be an important clue to disease elsewhere. Underlying causes are plenty and include drugs, congenital and acquired disorders of androgen and estrogen production, various tumors, renal failure, cirrhosis of the liver, and thyrotoxicosis. Evaluation includes a careful patient's history, physical examination of sexual characteristics and the breast tissue, and measurements of serum LH, FSH, testosterone, estradiol, hCG-beta, TSH and tests of liver and kidney function.

Growth hormone-releasing hormone and pituitary somatotrope proliferation

Growth hormone-releasing hormone (GHRH) is a hypothalamic hormone that is essential for normal expansion of the somatotrope lineage during pituitary development. Decreased GHRH secretion and/or action leads to impairment of this process and somatotrope hypoplasia in both humans and experimental animals. Excessive GHRH secretion and/or action result in dysregulated somatotrope proliferation, leading to hyperplasia and neoplastic transformation. Our understanding of the molecular and morphologic bases for these effects from both animal and clinical studies has greatly increased during the past decade. However, many features of the cellular pathways remain to be defined, including the interaction of other genes in the multistep process of somatotrope tumorigenesis.

Paraneoplastic syndromes associated with bronchogenic carcinoma

Paraneoplastic syndromes associated with lung cancer are diverse in their presentation, pathophysiology, and implications. They can be seen as a diagnostic and therapeutic challenge or as an opportunity to detect an otherwise asymptomatic malignancy. Unraveling the mechanisms that produce these syndromes will lead to insight into tumor biology that will be translated into novel approaches for early detection and therapy.

Long-acting lanreotide induces clinical and biochemical remission of acromegaly caused by disseminated growth hormone-releasing hormone-secreting carcinoid

Ectopic GHRH-secreting tumors, such as carcinoid, rarely cause acromegaly. As protracted exposure to high levels of GH is associated with considerable morbidity and mortality, these patients require early and effective medical therapy to control hormonal hypersecretion. We employed a prolonged release somatostatin analog, lanreotide, to treat a patient with disseminated GHRH-producing carcinoid. Before treatment, the patient had a biochemical profile characteristic of active acromegaly. Plasma GHRH levels were markedly elevated (200-fold), and urinary 5-hydroxyindolacetic acid (5-HIAA) levels were increased (4-fold). Magnetic resonance imaging revealed a large asymmetrical pituitary mass consistent with somatotroph hyperplasia. Somatostatin receptor scintigraphy revealed multiple bony and soft tissue lesions as well as striking pituitary uptake. Lanreotide (30 mg) was administered weekly by im injection for 12 weeks. Rapid and sustained symptomatic clinical improvement with diminished soft tissue swelling and hyperhidrosis was observed. GHRH levels decreased by 70%; glucose-suppressed GH and insulin-like growth factor I levels were reduced by 90% and 75%, respectively, to near normal values; urinary 5-HIAA levels normalized; and the pituitary mass remained unchanged. Unfortunately, the patient died due to complications of osteogenic sarcoma. In conclusion, prolonged release lanreotide induced clinical and biochemical remission in this patient with diffusely metastatic GHRH-producing carcinoid. This long-acting drug thus offers an effective, well tolerated, and convenient medical therapy for control of hormonal hypersecretion induced by excess GHRH.

Endocrine/metabolic syndromes of cancer

In addition to producing symptoms directly by their mass or invasion of tissues, cancers may also make themselves evident by the secretion of cytokines, protein hormones, or hormone precursors, which in turn, results in recognizable clinical syndromes. This article reviews the endocrine syndromes of cancer, their pathophysiologic basis, and the means of diagnosis. Many of these protein hormones appear to be produced in small amounts by normal tissues where they act in paracrine fashion as cytokines. Furthermore, neoplastic transformation is associated with continued, or often dramatically amplified, production of paracrine substances, permitting them to circulate in the blood and to act as hormones. Thus, classical definitions of cytokines and hormones become blurred. In this context, so-called "ectopic" cancer production is not ectopic, but rather a modification of normal cell function. The majority of the endocrine syndromes of cancer are caused by cancer production of these cytokines or hormones. Except for cancers originating in the adrenals or gonads, cancers do not synthesize steroids and secrete them, although very rarely a cancer may metabolize a normal steroid precursor to produce a biologically active steroid.

Carcinoid tumours

The use of long-acting and potent somatostatin analogues is a major advance in the management of carcinoid tumours. In addition to providing effective symptom relief in malignant carcinoid syndrome, octreotide can also be used for diagnostic purposes. Despite its expense, octreotide is the current agent of choice for the treatment of this condition while analogues with different receptor specificities and pharmacokinetics hold promise for the future. Gastric carcinoids have aroused interest because of their experimental association with chronic hypergastrinaemia, a condition now commonplace because of the widespread use of H2-blockers and proton-pump inhibitors. This subject is reviewed. The slow evolution of many tumours demands prolonged follow-up and the active use of a variety of palliative interventions. These include measures such as hepatic and cardiac surgery, which might be deemed inappropriate for patients with other types of metastatic malignancy. Interferons may have a role when first-line treatments have failed. Chemotherapy is, generally, of limited value.

Steroid cell tumor of the ovary as a rare cause of virilization

BACKGROUND

Virilization is associated with either ovarian causes, including polycystic ovary syndrome, hyperthecosis, and ovarian tumor, or with adrenal causes, including tumors and congenital adrenal hyperplasia. In establishing the diagnosis, levels of dehydroepiandresterone sulfate, testosterone, and 17 alpha-hydroxyprogesterone (17-OHP), with their response to dexamethasone treatment, should be assessed; and, where indicated, computerized tomography, ultrasound, and selective venous catheterization should be undertaken.

CASE REPORT AND RESULTS

A 21-year-old woman presented with a 17-year history of early accelerated linear growth and virilization. During this time, a putative diagnosis of nonclassic congenital adrenal hyperplasia had been made, and she had been treated with glucocorticoids, with no regression in virilization, for 8 years. On presentation to our group, the failure of low- and high-dose dexamethasone suppression tests to decrease blood levels of testosterone and 17-OHP, combined with a relatively low blood level of corticotropin, led us to investigate an androgen-secreting tumor of ovarian origin. When ultrasonography and computerized tomography of the ovaries and adrenal glands displayed no abnormality, selective venous catheterization was performed, revealing an abnormal ovarian-peripheral gradient for testosterone, 17-OHP, estradiol, and androstenedione in the right ovarian vein. On exploratory laparotomy, a neoplasm adjacent to the right ovary was resected and was found to be a steroid cell tumor of the ovary not otherwise specified, one of the rarest tumors causing virilization in children. Symptomatic resolution followed tumor removal.

CONCLUSION

Selective ovarian and adrenal venous catheterization for hormone assays is an efficient method of identification and localization of an androgen source in virilizing syndromes when noninvasive methods fail.

Comparison of thermoregulatory characteristics of patients with intra- and suprasellar pituitary adenomas

Thermoregulatory capabilities under physiologic cold and heat exposure of 37 patients with suprasellar pituitary adenomas (As) and 10 patients with intrasellar adenomas (Ai) were analyzed and compared to each other and to 13 controls (Ctr.) In Ai no shift of the thermoregulatory threshold temperatures was observed. In As the regulation was shifted to a 0.5 degrees C higher mean body temperature in 82% of the patients, indicating a "set-point" elevation. The accuracy of the regulation against thermal loads was maintained, the velocity was reduced. Postoperative examination of As revealed a normalisation of the "set-point". Modifications of the hypothalamic amine systems by the compressive effect of the suprasellar adenomas are discussed to be the most probable cause for the observed thermoregulatory alterations.

Ectopic aldosteronoma associated to another adrenocortical adenoma in the adrenal gland of the same side

The occurrence of tumors originating from aberrant adrenocortical tissue in ectopic site is very rare. Up to now only two cases of ectopic aldosterone-producing adenoma have been described. We have observed another case of ectopic aldosteronoma, located in the retrocaval region, laterally to the body of the 12th thoracic vertebra. This ectopic tumor was associated to another adrenocortical adenoma, in the adrenal gland of the same side. The diagnostic implications of this observation are discussed.

Ectopic acromegaly

Ectopic acromegaly is a rare syndrome (less than 1% of acromegalic patients) caused by ectopic growth hormone-releasing hormone (GHRH) or growth hormone (GH)-producing tumors. Its recognition is clinically important because acromegaly may be a symptom of an aggressive tumor, and different therapeutic approaches are required. Most cases are caused by either extra- or intracranial GHRH-producing tumors, whereas in rare instances the underlying disease is an ectopic GH-secreting tumor. The routine evaluation of circulating GHRH in all acromegalic patients may allow its early recognition, because plasma levels greater than 0.3 ng/mL are virtually diagnostic of a GHRH-producing tumor (frequently a bronchial or pancreatic carcinoid), whereas suppressed levels may suggest an ectopic GH-producing tumor. In addition to classic imaging techniques, whole body scintiscan with labeled octreotide may help in the localization of ectopic tumors. Surgical removal of the ectopic tumor is the therapy of choice, but it is not always feasible because patients often present with widespread metastases. Patients with GHRH-induced acromegaly benefit from the administration of the long-acting somatostatin analog, octreotide, which reduces GH, IGF-I, and GHRH, and may shrink the ectopic tumor, its metastases, and the secondary pituitary enlargement.

Neuroendocrinology: clinical and experimental

There have been several important publications concerning the aetiology of human pituitary tumours, in particular, delineating some of the gene mutations which may underlie this clinical problem. There have not been any major developments in clinical neuroendocrinology although advances have been made in the pharmacological development of dopaminergic drugs and the diagnosis of Cushing's disease.

[Adrenal gland disorders]

Adrenal diseases are generally rare but of variable manifestation and high diagnostic expenditure for definitive conformation of the disease in the individual case; therefore, the definitive diagnosis is often made by the specialist. On the other hand the supposed diagnosis, based on the knowledge of clinical symptoms, is frequently made by the nonspecialist who also initiates the first diagnostic steps in order to confirm or exclude the diagnosis. It is the aim of this survey to discuss not only the clinical symptoms of the most important adrenal diseases, but also the essential diagnostic steps in order to at least narrow down the diagnosis with as little expenditure as possible and to avoid a diagnostic maze.

[Hypophyseal dysfunction and tumors]

Some pituitary hormones secrete hormones while others do not. Nonsecreting tumors can interfere with normal pituitary hormone secretion and produce tumor symptoms and signs like headaches and visual field defects. The most frequent hormone-secreting tumors are prolactinomas. Growth hormone or ACTH or gonadotropin or gonadotropin-alpha and beta chain-producing tumors are less frequent, TSH producing tumors are extremely rare. The most important elements of the diagnostic work-up are clinical signs and symptoms, assessment of pituitary function (measurement of TSH, free T4, LH, FSH, oestradiol/free testosteron, growth hormone, IGF-1, prolactin, ACTH, Cortisol, serum and urine osmolality), CT and/or MRI and, in patients with large tumors, a visual field exam. The treatment of choice of pituitary tumors is often surgery. Alternative therapies are radiation treatment (in nonoperable patients or when hormone levels are persistently elevated after pituitary surgery) and drug treatment (dopamine agonists in hyperprolactinemia, somatostatin analogues in acromegaly). Pituitary hormone deficiencies are treated depending on the specific deficiency with thyroxine, cortisone, oestrogen/gestagen/testosterone gonadotropines or ADH analogues.

Ectopic secretion of neurohypophyseal peptides in patients with malignancy

A great deal of information has been accumulated on the synthesis and release of AVP, oxytocin, and their associated neurophysins under normal circumstances. In 1957, Schwartz and Bartter first described SIAD in patients with lung cancer and postulated that the clinical findings were the results of excessive vasopressin secretion. Tumors have been known since 1964 to produce vasopressin, and small cell (oat cell) carcinoma of the lung is by far the most frequent malignant cause of SIAD. The biosynthetic pathway for the synthesis of AVP and its associated neurophysin (and to a lesser extent, oxytocin and its neurophysin) is well described and is similar if not identical to the synthesis of these peptides in the hypothalamus. However, there is little reliable information on the control of peptide synthesis and release by these tumors. The clinical picture of SIAD is well described and occurs in 20% to 40% of patients with SCCL, although up to 88% of patients with extensive SCCL have elevated circulating levels of one or more neurohypophyseal peptides. This information has led to considerable interest in the use of these peptides as tumor markers for the diagnosis, evaluation, and assessment of therapy in these patients. With the recognition of the high incidence of secretion of neurohypophyseal peptides by SCCL, studies have been initiated to determine the value of radioactive vasopressin neurophysin antibodies in localizing tumors that synthesize these peptides. The studies provide potentially useful information in diagnosing and following patients with SCCL and also offer some promise that radiolabeled antineurophysins could eventually be used to treat these patients.

Extrapituitary acromegaly

Acromegaly may result from ectopic production of the hypothalamic peptide, growth hormone releasing hormone (GHRH), or growth hormone (GH) itself. Hypothalamic, carcinoid, and pancreatic tumors account for most of these cases. The pathogenesis, etiology, and diagnosis of acromegaly caused by these nonpituitary tumors is discussed, and an approach to their management is provided.

Tumor secretion of growth factors

An increasing number of polypeptide growth factors have been identified that regulate not only cell proliferation but also an extraordinary range of cell activities, including matrix protein deposition and resolution, the maintenance of cell viability, cell differentiation, inflammation, and tissue repair. Normal cells appear to require growth factors for proliferation and for maintenance of viability. Cells that secrete a polypeptide growth factor have an advantage in growth. These factors can act either externally through cell surface receptors or internally during the transport of receptors and growth factors through the endoplasmic reticulum and Golgi apparatus, causing autocrine stimulation of cell growth. Depending on the cell type, growth factors can also be potent inhibitors of cell growth rather than stimulators of growth, and the effect can depend on the presence or absence of growth factors. Among the growth factors considered, IGFs are unusual in that they function both as endocrine and as autocrine/paracrine agents. IGF-II, which is associated with fetal growth, is the IGF most frequently expressed by tumors. There is now convincing evidence that some tumors secrete sufficient IGF-II to have systemic endocrine effects as recognized as nonislet cell tumor hypoglycemia. PDGF is normally highly concentrated in platelets and has major significance in stimulation of cellular proliferation in inflammation and wound repair. Normally, this proliferation is self-limited, but the secretion of PDGF by tumors and its effects on cell proliferation of tumors persist. The fact that PDGF B monomer has an identical structure with that of the proto-oncogene C-cis further strengthens the connection between PDGF and tumor growth. EGF has a restricted role in normal physiology, but its close relative, TGF-alpha, is widely distributed in normal and neoplastic tissues. The common receptor for EGF and TGF-alpha is present in many normal and neoplastic cell types. The EGF receptor is the product of the C-erb gene. The oncogene V-cis is a truncated form of the EGF receptor whose tyrosine kinase activity is not dependent on ligand binding. TGF-beta exists in multiple forms. Although it can transform the morphology of certain cell lines in culture, it probably does not act generally as a mitogenic agent. Its major physiologic role in the body appears to be the stimulation of mesenchymal matrix formation. It is of special importance in the regulation of bone matrix formation. Its expression is increased in many tumors.(ABSTRACT TRUNCATED AT 400 WORDS)

Ectopic secretion of peptides of the proopiomelanocortin family

A wide spectrum of clinical and biochemical presentations characterize ectopic POMC syndrome. It is presently postulated that ectopic POMC production results from increased expression of the activity of a POMC gene normally occurring in a variety of tissues outside the pituitary gland. The syndrome is rapidly progressive and is characterized by severe clinical manifestations in patients with a more aggressively developing oat cell carcinoma of the lung. However, in patients with slower growing nonpituitary tumors, the presentation may overlap that seen in patients with pituitary ACTH-dependent Cushing's syndrome. In cases in which the biochemical testing results overlap with those seen in pituitary ACTH-dependent disease, a combination of lack of suppression with high-dose dexamethasone and absent response to CRH stimulation greatly increases the diagnostic accuracy. Abnormal alternative processing of POMC in nonpituitary neoplasms may render unusual POMC-derived peptides that could be used as markers in the diagnosis and follow-up of patients with this syndrome. The prognosis of patients afflicted with ectopic POMC syndrome is largely determined by the nature of the underlying tumor. However, the clinical course can be greatly modified by control of the metabolic manifestations of hypercortisolemia. A variety of surgical and pharmacologic options are available, including adrenalectomy and the use of adrenal inhibitors. Cushing's syndrome of long duration, the finding of ectopic pituitary adenomas, and the combined secretion of CRH and POMC by nonpituitary tumors constitute interesting variants of the classic picture.

The role of 1,25-dihydroxyvitamin D in the maintenance of hypercalcemia in a patient with an ovarian carcinoma producing parathyroid hormone-related protein

The syndrome of humoral hypercalcemia of malignancy (HHM) is thought to be mainly a result of the production of parathyroid hormone-related protein (PTHRP) by malignant tumors. Serum 1,25-dihydroxyvitamin D (1,25-DHD) concentrations are generally low in such patients, which contrasts with the findings in animal studies. A patient is reported with HHM from a clear cell ovarian carcinoma and elevated serum immunoreactive PTHRP (about five times the upper limit of normal) in whom serum 1,25-DHD concentrations were abnormally high (200 pmol/l) and associated with increased intestinal calcium absorption. Treatment with two different nitrogen-containing bisphosphonates (pamidronate and [3-dimethyl-amino-1-hydroxypropylidene]-1,1-bisphosphonate) did not normalize serum and urinary calcium despite effective inhibition of bone resorption. These observations suggested an additional intestinal contribution to the maintenance of hypercalcemia. Tumor removal was followed by decreases in serum immunoreactive PTHRP and 1,25-DHD concentrations to their respective normal ranges and normocalcemia. Separating HHM into Types I and II, according to the prevailing serum 1,25-DHD concentrations, can provide a basis for a better understanding of the pathogenesis of hypercalcemia, and it also may have practical use in the successful management of these patients.

The parathyroid hormone-related protein associated with malignancy is secreted by neuroendocrine tumors

We have demonstrated the production of the PTH-related protein (PTHrP) associated with hypercalcemia of malignancy by human neuroendocrine cell lines that also produce calcitonin gene products and chromogranin A. PTHrP was demonstrable in the cells by immunocytochemistry and immunoassay and Northern analysis of the cells revealed the presence of multiple mRNAs for PTHrP. The cell lines also secreted PTHrP in a regulated fashion, with the most potent secretagogue being phorbol. Thus, PTHrP is secreted by neuroendocrine cells and it may have neuroectodermal lineage. The coexpression of calcitonin gene products and chromogranin A, also neuroendocrine, with PTHRP may influence its secretion and ultimate biological effects in vivo.

Hormone-producing gastrointestinal tumors contain a high density of somatostatin receptors

Fourteen hormone-producing gastrointestinal tract tumors were tested for their content of somatostatin (SRIH) receptors, using receptor autoradiography and in vitro binding assay with tumor homogenates. All four gastrinomas tested had high levels of SRIH receptors, as did two of five insulinomas and four of five vasoactive intestinal peptide-producing tumors. Receptor visualization was obtained with two different radioligands, either a SRIH-28 analog, [125I]-[Leu8,D-Trp22,Tyr25]SRIH-28, or a SRIH octapeptide, the [125I]Tyr3 derivative of SMS 201-995 [H-DPhe-Cys-Phe-DTrp-Lys-Thr-Cys-Thr(ol)], [125I]204-090. In both cases receptors were localized over the tumor cell area only. Biochemical and pharmacological analyses of one insulinoma and two vipomas revealed saturable, high affinity binding sites with pharmacological specificity for SRIH. However, differences in receptor affinity of selected SRIH analogs, in particular SRIH-28 and SRIH octapeptides, were found between the insulinomas and the two other tumor types, vipoma and gastrinoma. The presence of SRIH receptors on various hormone-producing gastrointestinal tumors suggests that at least part of the beneficial effects of chronic therapy with SRIH analogs may be mediated through such membrane-bound receptors located on the tumor itself. SRIH receptor measurement may be of prognostic value in assessment of the therapeutic efficacy of SRIH analogs. They may also be of diagnostic value, if used as in vivo markers for the localization of small hormone-producing gastrointestinal tumors or their metastases.

Evidence for ectopic ACTH production years after bilateral adrenalectomy for Cushing's syndrome: in vivo and in vitro studies

Three patients presented with hyperpigmentation and high plasma levels of ACTH 4-5 years after bilateral adrenalectomy for Cushing's "disease". X-rays and ct-scan of the lungs showed a small pulmonary mass in all. ACTH levels (1100-2000 pg/ml) were not suppressible by high doses hydrocortisone. A carcinoid tumor was removed in two cases and a chemodectoma in the third. Evidence for ACTH secretion by these tumors was provided by both decrease of ACTH levels after surgery and/or in vitro studies. Both carcinoid cultures showed a basal ACTH production, which was clearly increased by LVP (10(-7) M) and CRF (10(-7) M). Our findings in vitro studies suggest the presence of specific receptor sites for physiological stimuli (LVP and CRF) in tumor cell membranes.

[Peptide hormones and the "new endocrinology"]

On the basis of the results found in literature a survey is given of the state of the peptide-chemical research from the point of view of the clinic. The functional mechanisms of the peptide hormones are explained, their effect as hormone and neurotransmitter is demonstrated. Particularly emphasized are the integrative tasks of the peptide hormones, which thus as another regulation principle of the organism are to be put by the side of the nervous and hormonal regulation. By the demonstration of the most frequent endocrine tumour syndromes with formation of adequate hormones the clinical importance of these substances is dealt with. The infrequency of these diseases is emphasized by the small number of own observations. It is referred to the growing importance of the peptide hormones in the diagnostics and therapy of internal and surgical diseases.