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

Severe Obesity Associated with Pituitary Corticotroph Hyperplasia and Neoplasia:

OBJECTIVE

Obesity is associated with hypercortisolism. The incidence of corticotroph hyperplasia or lymphocyte infiltration in the pituitary of patients with obesity is unknown.

METHODS

Pituitary and adrenal glands from 161 adult autopsies performed between 2010 and 2019 at our institution were reviewed. Clinical history, body mass index, and cause of death were recorded Routine hematoxylin & eosin, reticulin and immunohistochemical stains for ACTH, CD3, and CD20 were done. Results were analyzed using Fisher and Chi-square statistics.Decedents were separated into 4 groups based on BMI (kg/m²): Lean (BMI <25.0), Overweight (BMI of 25.0 to 29.9), Obesity Class I (BMI of 30.0 to 34.9), and Obesity Class II-III (BMI > 34.9).

RESULTS

Corticotroph hyperplasia/neoplasia was identified in 44 of 161 pituitary glands. 4 of 53 (9.1%) lean patients had pituitary lesions whereas 27.3% (12) of overweight, 22.7% (10) of obesity class I and 40.9% (18) of obesity class II patients had hyperplasia (p < 0.0001). Small corticotroph tumors were identified in 15 patients; only one was a lean patient and the tumor was associated with Crooke's hyaline change of nontumorous corticotrophs. The presence of corticotroph hyperplasia and neoplasia was associated with adrenal cortical hyperplasia and lipid depletion. Microscopic foci of T lymphocytes and B lymphocytes were identified in pituitaries of patients within each weight category; no independent association between BMI and lymphocytic inflammation was found.

CONCLUSION

Our data indicate an association between corticotroph hyperplasia/neoplasia and obesity. It remains unclear whether obesity is the cause or effect of ACTH and cortisol excess.

An ectopic Cushing's syndrome as a cause of severe refractory hypokalemia in the ICU

Background: Ectopic Cushing's syndrome is a very rare condition caused by an ACTH-secreting tumor outside the pituitary or adrenal glands, and the majority of these cases are encountered in the context of paraneoplastic syndromes. The ectopic source of ACTH secretion is not always obvious to detection and can be challenging. We report a rare case, in which a hidden ACTH-secreting carcinoid tumor of the lung caused a severe refractory hypokalemia, leading us to a race against time to locate the tumor.Case presentation: A 33-year-old young male was admitted to the ICU for the management of a severe hypokalemia, and complains from several months of depression, increased weight, disabling non-radiating dorsal lower back pain and refractory arterial hypertension. The physical examination immediately suggested a Cushing's syndrome. The 24-h cortisoluria confirmed hypercortisolism and the increased ACTH level was oriented towards ACTH-dependent Cushing's syndrome. Thereafter, a dexamethasone suppression test was negative, indicating in favor of ectopic ACTH secretion. The etiological assessment via imaging and isotopes revealed a solitary pulmonary nodule at the right lower lobe estimated at 18 mm, the resection and anatomopathological analysis of which led to the diagnosis of carcinoid pulmonary tumor, and resolved hypercortisolism and its complications.Conclusion: A delayed diagnosis of Cushing's syndrome result in a consequent morbi-mortality, mainly due to cardiovascular events. The optimal treatment for ectopic Cushing's syndrome is surgical resection, thus making the localization of the tumor a key element.

Corticotroph hyperplasia and Cushing disease: diagnostic features and surgical management

OBJECTIVE

This study was done to compare corticotroph hyperplasia and histopathologically proven adenomas in patients with Cushing disease by analyzing diagnostic features, surgical management, and clinical outcomes.

METHODS

Patients with suspected pituitary Cushing disease were included in a retrospective cohort study and were excluded if results of pathological analysis of the surgical specimen were nondiagnostic or normal. Cases were reviewed by two experienced neuropathologists. Total lesion removal was used as a dichotomized surgical variable; it was defined as an extracapsular resection (including a rim of normal gland) in patients with an adenoma, and for hyperplasia patients it was defined as removal of the presumed lesion plus a rim of surrounding normal gland. Bivariate and multivariate analyses were performed. Recurrence-free survival was compared between the two groups.

RESULTS

The final cohort consisted of 63 patients (15 with hyperplasia and 48 with adenoma). Normal pituitary acinar architecture was highly variable. Corticotroph hyperplasia was diagnosed based on the presence of expanded acini showing retained reticulin architecture and predominant staining for adrenocorticotropic hormone. Crooke's hyaline change was seen in 46.7% of specimens, and its frequency was equal in nonlesional tissue of both groups. The two groups differed only by MRI findings (equivocal/diffuse lesion in 46% of hyperplasia and 17% of adenoma; p = 0.03). Diagnostic uncertainty in the hyperplasia group resulted in additional confirmatory testing by 24-hour urinary free cortisol. Total lesion removal was infrequent in patients with hyperplasia compared to those with adenoma (33% vs 65%; p = 0.03). Initial biochemical remission was similar (67% in hyperplasia and 85% in adenoma; p = 0.11). There was no difference in hypothalamic-pituitary-adrenal axis recovery or disease recurrence. The median follow-up was 1.9 years (IQR 0.7-7.6 years) for the hyperplasia group and 1.2 years (IQR 0.4-2.4 years) for the adenoma group. Lack of a discrete lesion and diagnostic uncertainty were the only significant predictors of hyperplasia (sensitivity 53.3%, specificity 97.7%, positive predictive value 88.9%, negative predictive value 85.7%). An adjusted Cox proportional hazards model showed similar recurrence-free survival in the two groups.

CONCLUSIONS

This study suggests an association between biochemically proven Cushing disease and histopathologically proven corticotroph hyperplasia. Imaging and operative findings can be ambiguous, and, compared to typical adenomas with a pseudocapsule, the surgical approach is more nuanced. Nevertheless, if treated appropriately, biochemical outcomes may be similar.

An opponent process for alcohol addiction based on changes in endocrine gland mass

Consuming addictive drugs is often initially pleasurable, but escalating drug intake eventually recruits physiological anti-reward systems called opponent processes that cause tolerance and withdrawal symptoms. Opponent processes are fundamental for the addiction process, but their physiological basis is not fully characterized. Here, we propose an opponent processes mechanism centered on the endocrine stress response, the hypothalamic-pituitary-adrenal (HPA) axis. We focus on alcohol addiction, where the HPA axis is activated and secretes β-endorphin, causing euphoria and analgesia. Using a mathematical model, we show that slow changes in the functional mass of HPA glands act as an opponent process for β-endorphin secretion. The model explains hormone dynamics in alcohol addiction and experiments on alcohol preference in rodents. The opponent process is based on fold-change detection (FCD) where β-endorphin responses are relative rather than absolute; FCD confers vulnerability to addiction but has adaptive roles for learning. Our model suggests gland mass changes as potential targets for intervention in addiction.

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Addiction involves tolerance and withdrawal over weeks

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Model of the HPA-axis and β-endorphins explains tolerance and withdrawal

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Effects due to changes in the functional mass of endocrine glands

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Fold-change detection makes circuit prone to addiction but boosts learning

A new model for the HPA axis explains dysregulation of stress hormones on the timescale of weeks

Stress activates a complex network of hormones known as the hypothalamic-pituitary-adrenal (HPA) axis. The HPA axis is dysregulated in chronic stress and psychiatric disorders, but the origin of this dysregulation is unclear and cannot be explained by current HPA models. To address this, we developed a mathematical model for the HPA axis that incorporates changes in the total functional mass of the HPA hormone-secreting glands. The mass changes are caused by HPA hormones which act as growth factors for the glands in the axis. We find that the HPA axis shows the property of dynamical compensation, where gland masses adjust over weeks to buffer variation in physiological parameters. These mass changes explain the experimental findings on dysregulation of cortisol and ACTH dynamics in alcoholism, anorexia, and postpartum. Dysregulation occurs for a wide range of parameters and is exacerbated by impaired glucocorticoid receptor (GR) feedback, providing an explanation for the implication of GR in mood disorders. These findings suggest that gland-mass dynamics may play an important role in the pathophysiology of stress-related disorders.

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.

Molecular analysis and literature-based hypothesis of an immunonegative prostate small cell carcinoma causing ectopic ACTH syndrome

Ectopic ACTH syndrome (EAS) due to a prostate small cell carcinoma (SCC) is very rare with only 26 cases reported to date and has a poor prognosis. We here describe another case of this disorder that was clinically typical based on prior reports as it showed hypercortisolemia and severe hypokalemia with multiple metastasis. However, our current case of prostate SCC causing EAS is the first to display negative immunostaining for ACTH despite detectable POMC mRNA expression in the primary lesion. ACTH immunonegativity is thought to be associated with a more aggressive disease course and a poorer prognosis although there are few studies of the underlying mechanisms. We explored two possibilities for this finding in our current patient: aberrant POMC processing prevented immunodetection with an anti-ACTH antibody; and the ACTH content per cell was below the threshold for immunodetection due to its rapid secretion or low synthesis. The aberrant processing theory was thought to be less likely because of immunonegative findings even using anti-POMC/ACTH antibodies. As the plasma ACTH levels in our patient were comparable with those reported for previous immunopositive prostate EAS cases, we speculated that the depletion of ACTH may be caused not only by rapid secretion but also by low production levels as a sign of de-differentiation. De-differentiation may therefore explain the mechanism underlying the negative correlation between immunoreactivity for ACTH in EAS and disease aggressiveness. We believe that our present findings will be of use in future prospective studies aimed at confirming the mechanism of immunonegativity.

Dual Paraneoplastic Endocrine Syndromes Heralding Onset of Extrapulmonary Small Cell Carcinoma: A Case Report and Narrative Review

OBJECTIVE

Extrapulmonary small cell carcinoma (EPSCC) is rare and frequent metastases at presentation can complicate efforts to identify a site of origin. In particular, SCC comprises <1% of prostate cancers and has been implicated in castration resistance.

METHODS

Clinical, laboratory, imaging, and pathology data are presented.

RESULTS

A 56-year-old man with locally advanced prostate adenocarcinoma on androgen deprivation therapy presented with a clogged nephrostomy tube. Laboratory results included calcium 13.8 mg/dL (8.5-10.5 mg/dL), albumin 3.6 g/dL (3.5-5 mg/dL), and potassium 2.8 mmol/L (3.5-5.2 mmol/L). Hypercalcemia investigation revealed intact PTH 19 pg/mL (16-87 pg/mL), 25-OH vitamin D 15.7 ng/mL (>30 ng/mL), and PTH-related peptide (PTHrP) 63.4 pmol/L (<2.3 pmol/L). Workup for hypokalemia yielded aldosterone 5.3 ng/dL (<31 ng/dL), renin 0.6 ng/mL/h (0.5-4 ng/mL/h), and 6:00 a.m. cortisol 82 µg/dL (6.7-22.6 µg/dL) with ACTH 147 pg/mL (no ref. range). High-dose Dexamethasone suppression testing suggested ACTH-dependent ectopic hypercortisolism. Contrast-enhanced CT findings included masses in the liver and right renal pelvis, a heterogeneous enlarged mass in the region of the prostate invading the bladder, bilateral adrenal thickening, and lytic lesions in the pelvis and spine. Liver biopsy identified epithelioid malignancy with Ki proliferation index 98% and immunohistochemical staining positive for synaptophysin and neuron-specific enolase, compatible with high-grade small cell carcinoma. Staining for ACTH was negative; no stain for CRH was available. Two weeks after chemotherapy, 6:00 a.m. cortisol normalized and CT scans showed universal improvement.

CONCLUSION

Extensive literature details paraneoplastic syndromes associated with SCC, but we report the first case of EPSCC diagnosed due to onset of dual paraneoplastic syndromes.

A rare case of an ACTH/CRH co-secreting midgut neuroendocrine tumor mimicking Cushing's disease

Ectopic ACTH/CRH co-secreting tumors are a very rare cause of Cushing’s syndrome and only a few cases have been reported in the literature. Differentiating between Cushing’s disease and ectopic Cushing’s syndrome may be particularly difficult if predominant ectopic CRH secretion leads to pituitary corticotroph hyperplasia that may mimic Cushing’s disease during dynamic testing with both dexamethasone and CRH as well as bilateral inferior petrosal sinus sampling (BIPSS). We present the case of a 24-year-old man diagnosed with ACTH-dependent Cushing’s syndrome caused by an ACTH/CRH co-secreting midgut NET. Both high-dose dexamethasone testing and BIPSS suggested Cushing’s disease. However, the clinical presentation with a rather rapid onset of cushingoid features, hyperpigmentation and hypokalemia led to the consideration of ectopic ACTH/CRH-secretion and prompted a further workup. Computed tomography (CT) of the abdomen revealed a cecal mass which was identified as a predominantly CRH-secreting neuroendocrine tumor. To the best of our knowledge, this is the first reported case of an ACTH/CRH co-secreting tumor of the cecum presenting with biochemical features suggestive of Cushing’s disease.

Severe Cushing's syndrome due to small cell prostate carcinoma: a case and review of literature

Cushing's syndrome (CS) due to ectopic adrenocorticotrophic hormone (ACTH) is associated with a variety of tumours most of which arise in the thorax or abdomen. Prostate carcinoma is a rare but important cause of rapidly progressive CS. To report a case of severe CS due to ACTH production from prostate neuroendocrine carcinoma and summarise previous published cases. A 71-year-old male presented with profound hypokalaemia, oedema and new onset hypertension. The patient reported two weeks of weight gain, muscle weakness, labile mood and insomnia. CS due to ectopic ACTH production was confirmed with failure to suppress cortisol levels following low- and high-dose dexamethasone suppression tests in the presence of a markedly elevated ACTH and a normal pituitary MRI. Computed tomography demonstrated an enlarged prostate with features of malignancy, confirmed by MRI. Subsequent prostatic biopsy confirmed neuroendocrine carcinoma of small cell type and conventional adenocarcinoma of the prostate. Adrenal steroidogenesis blockade was commenced using ketoconazole and metyrapone. Complete biochemical control of CS and evidence of disease regression on imaging occurred after four cycles of chemotherapy with carboplatin and etoposide. By the sixth cycle, the patient demonstrated radiological progression followed by recurrence of CS and died nine months after initial presentation. Prostate neuroendocrine carcinoma is a rare cause of CS that can be rapidly fatal, and early aggressive treatment of the CS is important. In CS where the cause of EAS is unable to be identified, a pelvic source should be considered and imaging of the pelvis carefully reviewed.

Unusual Cushing's Syndrome and Hypercalcitoninaemia due to a Small Cell Prostate Carcinoma

A 75-year-old man was hospitalized because of severe hypokalaemia due to ACTH dependent Cushing's syndrome. Total body computed tomography (TBCT) and 68 Gallium DOTATATE PET/CT localized a voluminous prostate tumour. A subsequent transurethral prostate biopsy documented a small cell carcinoma positive for ACTH and calcitonin and negative for prostatic specific antigen (PSA) at immunocytochemical study; serum prostatic specific antigen (PSA) was normal. Despite medical treatments, Cushing's syndrome was not controlled and the patient's clinical condition progressively worsened. Surgical resection was excluded; the patient underwent a cycle of chemotherapy followed by febrile neutropenia and fatal intestinal perforation. This case report describes a rare case of Cushing's syndrome and hypercalcitoninaemia due to a small cell carcinoma of the prostate, a rare tumour with very few therapeutic options and negative prognosis.

Phaeochromocytoma and ACTH-dependent cushing's syndrome: tumour crf secretion can mimic pituitary cushing's disease

INTRODUCTION

10% of corticotrophin (ACTH)-dependent Cushing's syndrome arises from secretion by extrapituitary tumours, with phaeochromocytoma implicated in a few cases. Ectopic secretion by phaeochromocytoma of corticotropin-releasing hormone (CRF), with secondary corticotroph hyperplasia, is even rarer, with only five cases in the literature hitherto. However, such cases may be classified as 'ectopic ACTH' due to incomplete verification.

CLINICAL CASES

We describe three patients with phaeochromocytoma and ACTH-dependent Cushing's syndrome in whom biochemical cure was achieved following unilateral adrenalectomy. Although unable to access a validated CRF assay within the timeframe for sample storage, we nevertheless inferred CRF secretion in 2 of 3 cases by tumour immunostaining (positive for CRF; negative for ACTH), supported in one case by pre-operative inferior petrosal sinus sampling (IPSS) indicative of pituitary ACTH source. Both cases were characterized by rapid postoperative wean off glucocorticoids, presumed to reflect the pituitary stimulatory-effect of CRF outweighing central negative feedback inhibition by hypercortisolaemia. By contrast, the tumour excised in a third case exhibited positive immunostaining for ACTH - negative for CRF - and postoperative recovery of hypothalamic-pituitary-adrenal axis took significantly longer.

DISCUSSION

Ectopic CRF production is biochemically indistinguishable from ectopic ACTH secretion, except that IPSS mimics pituitary Cushing's disease and cortisol dynamics may normalize rapidly postadrenalectomy. CRF secretion can be inferred through tumour immunohistochemistry, even if no CRF assay is available. Unrecognized phaeochromocytoma ACTH secretion may underpin some cases of cardiovascular collapse postadrenalectomy through acute hypocortisolaemia. Despite advances in phaeochromocytoma genetics since previous reports, we were unable to identify somatic DNA defects associated with either ACTH or CRF secretion.

Small cell carcinoma of the prostate presenting with Cushing Syndrome. A narrative review of an uncommon condition

Small cell carcinoma (SCC) of the prostate is an uncommon condition; there are very few cases in which presenting symptoms are consistent with Cushing Syndrome (CS). We report a new case in which CS triggers the suspicion of an SCC of the prostate and a review of the published cases of SCC of the prostate presenting with CS. The origin of these neoplasms is still unclear. It may be suspected when laboratory features appear in patients diagnosed with prostatic adenocarcinoma which becomes resistant to specific therapy. SCC usually occurs after the 6th decade. Patients suffering SCC of the prostate presenting with CS usually present symptoms such as hypertension, hyperglycemia, alkalosis or hypokalemia; cushingoid phenotype is less frequent. Cortisol and ACTH levels are often high. Prostatic-specific antigen levels are usually normal. CT scan is the preferred imaging test to localize the lesion, but its performance may be improved by adding other tests, such as FDG-PET scan. All patients have metastatic disease at the time of diagnosis. Lymph nodes, liver and bone are the most frequent metastases sites. Surgery and Ketokonazole are the preferred treatments for CS. The prognosis is very poor: 2- and 5-year survival rates are 27.5 and 14.3%, respectively. Key messages When a patient presents with ectopic Cushing Syndrome but lungs are normal, an atypical localization should be suspected. We should suspect a prostatic origin if Cushing Syndrome is accompanied by obstructive inferior urinary tract symptoms or in the setting of a prostatic adenocarcinoma with rapid clinical and radiological progression with relatively low PSA levels. Although no imaging test is preferred to localize these tumors, FDG-PET-TC can be very useful. Hormone marker scintigraphy (e.g. somatostatin) could be used too. As Cushing Syndrome is a paraneoplastic phenomenon, treatment of the underlying disease may help control hypercortisolism manifestations. These tumors are usually metastatic by the time of diagnosis. They have very poor prognosis.

Nelson's syndrome: a review of the clinical manifestations, pathophysiology, and treatment strategies

Nelson's syndrome is a rare clinical manifestation that occurs in 8%-47% of patients as a complication of bilateral adrenalectomy, a procedure that is used to control hypercortisolism in patients with Cushing's disease. First described in 1958 by Dr. Don Nelson, the disease has since become associated with a clinical triad of hyperpigmentation, excessive adrenocorticotropin secretion, and a corticotroph adenoma. Even so, for the past several years the diagnostic criteria and management of Nelson's syndrome have been inadequately studied. The primary treatment for Nelson's syndrome is transsphenoidal surgery. Other stand-alone therapies, which in many cases have been used as adjuvant treatments with surgery, include radiotherapy, radiosurgery, and pharmacotherapy. Prophylactic radiotherapy at the time of bilateral adrenalectomy can prevent Nelson's syndrome (protective effect). The most promising pharmacological agents are temozolomide, octreotide, and pasireotide, but these agents are often administered after transsphenoidal surgery. In murine models, rosiglitazone has shown some efficacy, but these results have not yet been found in human studies. In this article, the authors review the clinical manifestations, pathophysiology, diagnostic criteria, and efficacy of multimodal treatment strategies for Nelson's syndrome.

Pitfalls in the diagnosis and management of Cushing's syndrome

Despite many recent advances, the management of patients with Cushing's disease continues to be challenging. Cushing's syndrome is a complex metabolic disorder that is a result of excess glucocorticoids. Excluding the exogenous causes, adrenocorticotropic hormone-secreting pituitary adenomas account for nearly 70% of all cases of Cushing's syndrome. The suspicion, diagnosis, and differential diagnosis require a logical systematic approach with attention paid to key details at each investigational step. A diagnosis of endogenous Cushing's syndrome is usually suspected in patients with clinical symptoms and confirmed by using multiple biochemical tests. Each of the biochemical tests used to establish the diagnosis has limitations that need to be considered for proper interpretation. Although some tests determine the total daily urinary excretion of cortisol, many others rely on measurements of serum cortisol at baseline and after stimulation (e.g., after corticotropin-releasing hormone) or suppression (e.g., dexamethasone) with agents that influence the hypothalamic-pituitary-adrenal axis. Other tests (e.g., measurements of late-night salivary cortisol concentration) rely on alterations in the diurnal rhythm of cortisol secretion. Because more than 90% of the cortisol in the circulation is protein bound, any alteration in the binding proteins (transcortin and albumin) will automatically influence the measured level and confound the interpretation of stimulation and suppression data, which are the basis for establishing the diagnosis of Cushing's syndrome. Although measuring late-night salivary cortisol seems to be an excellent initial test for hypercortisolism, it may be confounded by poor sampling methods and contamination. Measurements of 24-hour urinary free-cortisol excretion could be misleading in the presence of some pathological and physiological conditions. Dexamethasone suppression tests can be affected by illnesses that alter the absorption of the drug (e.g., malabsorption, celiac disease) and by the concurrent use of medications that interfere with its metabolism (e.g., inducers and inhibitors of the P450 enzyme system). In this review, the authors aim to review the pitfalls commonly encountered in the workup of patients suspected to have hypercortisolism. The optimal diagnosis and therapy for patients with Cushing's disease require the thorough and close coordination and involvement of all members of the management team.

Change in the immunophenotype of a somatotroph adenoma resulting in gigantism

BACKGROUND

Examining the pathologic progression of a pituitary adenoma from the point of a prepubescent child to an adult with gigantism affords us an opportunity to consider why patients may develop secretory or functioning tumors and raises questions about whether therapeutic interventions and surveillance strategies could be made to avoid irreversible phenotypic changes.

CASE DESCRIPTION

A patient underwent a sublabial transsphenoidal resection for a clinically non-functioning macroadenoma in 1999. He underwent radiation treatment and was transiently given growth hormone (GH) supplementation as an adolescent. His growth rapidly traversed several percentiles and he was found to have elevated GH levels. The patient became symptomatic and was taken for a second neurosurgical procedure. Pathology and immunohistochemical staining demonstrated a significantly higher proportion of somatotroph cells and dense granularity; he was diagnosed with a functional somatotroph adenoma.

CONCLUSIONS

While it is likely that the described observations reflect the manifestations of a functional somatotroph adenoma in development, it is possible that pubertal growth, GH supplementation, its removal, or radiation therapy contributed to the described endocrine and pathologic changes.

Corticotropin-releasing hormone receptors mediate apoptosis via cytosolic calcium-dependent phospholipase A₂ and migration in prostate cancer cell RM-1

Peripheral corticotropin-releasing hormone receptors (CRHRs) are G protein-coupled receptors that play different roles depending on tissue types. Previously, we discovered the mechanism of CRHR-mediated apoptosis of mouse prostate cancer cell line (RM-1) to be a change of Bcl-2:Bax ratio, and CRH was found to inhibit transforming growth factor β migration of breast cancer cells via CRHRs. In the present study, we investigated cytosolic calcium-dependent phospholipase A2 (cPLA2) bridging CRHR activations and Bcl-2:Bax ratio and the effect of CRHR activation on cell migration. Silencing of cPLA2 attenuated a CRHR1 agonist, CRH-induced apoptosis, and the decrease of the Bcl-2:Bax ratio, whereas silencing of cPLA2 aggravated CRHR2 agonist, Urocortin 2 (Ucn2)-inhibited apoptosis, and the increase of the Bcl-2:Bax ratio. CRH in a time- and concentration-dependent manner increased cPLA2 expression mainly through interleukin 1β (IL1β) upregulation. Ucn2 decreased cPLA2 expression through neither tumor necrosis factor α nor IL1β. CRH-suppressed decay of cPLA2 mRNA and Ucn2 merely suppressed its production. Overexpression of CRHR1 or CRHR2 in HEK293 cells correspondingly upregulated or downregulated cPLA2 expression after CRH or Ucn2 stimulation respectively. In addition, both CRH and Ucn2 induced migration of RM-1 cells. Our observation not only established a relationship between CRHRs and cell migration but also for the first time, to our knowledge, demonstrated that cPLA2 participates in CRHR1-induced apoptosis and CRHR2-inhibited apoptosis.

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia with a central and peripheral carcinoid and multiple tumorlets: a case report emphasizing the role of neuropeptide hormones and human gonadotropin-alpha

We report a case of diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH). We performed immunohistochemical analysis of 17 neuropeptides and human gonadotropin-alpha (hCGα), a trophoblastic peptide that promotes the proliferation of neuroendocrine cells. A 51-year-old woman with no history of smoking was found to have a nodule in the right middle lobe. Upon examination, the nodule was found to comprise diffuse linear and nodular neuroendocrine cell hyperplasia (NECH), numerous pulmonary tumorlets merging with one peripheral carcinoid, and an additional central carcinoid. Immunohistochemical analysis revealed diffuse but intense expression of the general neuroendocrine markers CD56, synaptophysin, and chromogranin A, together with gastrin-releasing peptide (GRP), calcitonin, and hCGα throughout the carcinoids, tumorlets, and NECH. Positive staining was also noted for adrenocorticotropic hormone, corticotropin-releasing hormone, met-enkephalin, vasoactive intestinal polypeptide, neurotensin, and growth hormone-releasing hormone in a few isolated cells of the carcinoids and the tumorlets, but staining for these proteins was entirely negative in the NECH lesions. The presence of these neuropeptides in neuroendocrine tumors might explain the presence of neuropeptide-producing tumors of the lungs, cases of which have been reported over the last 30 years. The preoperative serum proGRP level was high but returned to normal after surgical intervention, indicating that GRP was produced and secreted by carcinoids, tumorlets, and/or NECH lesions. It is also probable that neuroendocrine cells secreted GRP into the interstitium in a paracrine manner, leading to the development of dense fibrosis around the tumorlets. During the preoperative and postoperative periods, no evidence of bronchiolitis obliterans was noted, in contrast to some previously reported cases of DIPNECH.

Neuroendocrine carcinoma of the thyroid causing adrenocorticotrophic hormone-dependent Cushing's syndrome

BACKGROUND

Cushing's syndrome (CS) due to ectopic adrenocorticotrophic hormone (ACTH) and/or ectopic corticotropic releasing hormone (CRH) secretion accounts for <10% of all CS. Neuroendocrine carcinomas rarely cause CS. These carcinomas have been found to secrete either ACTH or rarely CRH. Herein we report a case of neuroendocrine carcinoma originating from the thyroid as the source of ACTH-dependent CS.

SUMMARY

A 30-year-old woman with features of CS presented with severe respiratory distress. Six months before that, she was diagnosed with primary hypothyroidism and started on levothyroxine (LT4) therapy. Biochemical evaluation was done, and nonsuppressed serum cortisol levels following dexamethasone with high ACTH confirmed a diagnosis of ACTH-dependent CS. Magnetic resonance imaging of the brain showed a bulky pituitary gland. Adrenal imaging showed bilateral adrenal hyperplasia. A computerized tomography scan showed a large anterior mediastinal mass arising from the neck and extending behind the transverse aortic arch. She underwent emergency thoracotomy due to rapidly progressive superior mediastinal syndrome and left vocal cord palsy. At surgery, the mass was seen originating from the thyroid and the thymus was compressed posteriorly. Near total thyroidectomy and thymectomy with removal of pericardial seedlings were done. Histopathology revealed sheets, cords, and nests of round or oval tumor cells with hyperchromatic nuclei and scant cytoplasm with local invasion and lymphovascular embolization suggestive of a neuroendocrine carcinoma arising from thyroid, staining positive for cytokeratin, synaptophysin, and chromogranin-A, and negative for calcitonin and carcinoembryonic antigen.

CONCLUSIONS

Here we report a case of a neuroendocrine tumor of the thyroid causing ACTH-dependent CS. The tumor was negative for calcitonin staining, indicating that this was not a medullary carcinoma of the thyroid. Neuroendocrine carcinomas originating from the thyroid gland are very rare. A thyroid tumor of neuroendocrine origin causing ACTH-dependent CS has not been reported previously.

Corticomedullary mixed tumor of the adrenal gland-a clinical and pathological chameleon: case report and review of literature

Adrenal tumors mostly present with specific and unique clinical features, regarding their endocrine metabolism. A 53-year-old man came to our Department for a left adrenal mass discovered incidentally. Biochemical and imaging findings were suspicious for a pheochromocytoma. The patient underwent a laparoscopic left adrenalectomy. A well-circumscribed 5.5-cm mass was removed. It was composed of adrenal cells intimately admixed with pheochromocytes. Immunohistochemical studies were positive both for cortical cells (inibin-α, synaptophysine and melan-A) and medullary cells (S-100 and chromogranine A). Final pathology was of corticomedullary mixed tumor (CMT). CMT is a rare tumor with 14 cases previously reported in literature, with wide variable biochemical behavior, such as his radiological and pathological features. Prevalence and actual malignant potential are yet unknown to our knowledge.

Nelson's syndrome

Nelson's syndrome is a potentially life-threatening condition that does not infrequently develop following total bilateral adrenalectomy (TBA) for the treatment of Cushing's disease. In this review article, we discuss some controversial aspects of Nelson's syndrome including diagnosis, predictive factors, aetiology, pathology and management based on data from the existing literature and the experience of our own tertiary centre. Definitive diagnostic criteria for Nelson's syndrome are lacking. We argue in favour of a new set of criteria. We propose that Nelson's syndrome should be diagnosed in any patient with prior TBA for the treatment of Cushing's disease and with at least one of the following criteria: i) an expanding pituitary mass lesion compared with pre-TBA images; ii) an elevated 0800 h plasma level of ACTH (>500 ng/l) in addition to progressive elevations of ACTH (a rise of >30%) on at least three consecutive occasions. Regarding predictive factors for the development of Nelson's syndrome post TBA, current evidence favours the presence of residual pituitary tumour on magnetic resonance imaging (MRI) post transsphenoidal surgery (TSS); an aggressive subtype of corticotrophinoma (based on MRI growth rapidity and histology of TSS samples); lack of prophylactic neoadjuvant pituitary radiotherapy at the time of TBA and a rapid rise of ACTH levels in year 1 post TBA. Finally, more studies are needed to assess the efficacy of therapeutic strategies in Nelson's syndrome, including the alkylating agent, temozolomide, which holds promise as a novel and effective therapeutic agent in the treatment of associated aggressive corticotroph tumours. It is timely to review these controversies and to suggest guidelines for future audit.

Severe hypertension and hypokalemia as first clinical manifestations in ectopic Cushing's syndrome

Ectopic ACTH production occurs in about 10% of all cases of Cushing's syndrome, and about 25% of cases of ACTH-dependent Cushing's syndrome. Diverse tumor types are able to produce ACTH ectopically, including small cell lung carcinoma. Ectopic ACTH secretion by malignant neoplasm has been reported to have earlier and more aggressive metabolic effects. We report a 59-year-old male patient with severe hypertension, metabolic alkalosis and hypokalemia as the first clinical manifestations of an ACTH-secreting small cell lung carcinoma, although the typical phenotypic features of Cushing's syndrome were not present. Ectopic Cushing's syndrome should always be ruled out in patients with severe hypertension and hypokalemia.

The pathogenesis of pituitary tumors

Recently there has been significant progress in our understanding of pituitary development, physiology, and pathology. New information has helped to clarify the classification of pituitary tumors. Epidemiologic analyses have identified a much higher incidence of pituitary tumors than previously thought. We review the pathogenetic factors that have been implicated in pituitary tumorigenesis and the application of novel targeted therapies that underscore the increasingly important role of the pathologist in determining accurate diagnoses and facilitating appropriate treatment of patients with these disorders.

Corticomedullary mixed adrenal tumor: case report and literature review

We report a 66-year-old woman with a mixed corticomedullary tumor of the left adrenal gland. The patient was found to harbor an adrenal incidentaloma while investigated for a spigelian hernia. Due to the atypical radiological features and the relatively large size of the adrenal lesion she underwent a left adrenalectomy following endocrine testing to exclude a functional lesion. Subclinical Cushing's syndrome was suggested by the failure to obtain adequate cortisol suppression (less than 1.8 microg/dL) following dexamethasone administration pre-operatively; cortisol suppression was restored postoperatively following the excision of the tumor. Histology was consistent with a corticomedullary mixed adenoma, a lesion for which, there is paucity of published data regarding its natural history and long term outcome. The finding of this case highlights the importance of this extremely rare entity which should be included in the long list of causes of adrenal incidentaloma since cases with intra-operative complications have been described. The previously reported reappearance of this tumor in the contralateral adrenal gland emphasizes the need for prolonged follow-up.

No pituitary gland volume change in medication-free depressed patients

Increased serum cortisol levels and a hyperactive hypothalamo-pituitary-adrenal (HPA) axis have been proposed to play an important role in the pathophysiology of Major Depressive Disorder (MDD). However, there are inconsistent results regarding pituitary gland volume (PGV), which is one of the key elements of the HPA axis evaluated by MRI in depressed patients. In this study, we analyzed the PGV of medication-free moderately depressed MDD patients (N=34) and age and sex matched healthy controls (N=39). PGV did not differ between MDD patients and healthy controls [mean volume+/-S.D.; 0.76+/-0.17 cm3 and 0.75+/-0.14 cm3; ANCOVA, F1,69=1.25 p>0.05; respectively]. Our results confirm that volumetric PGV changes are not crucial for depression pathophysiology among unmedicated, moderately depressed adults.

The role of corticotropin-releasing factor in the investigation of endocrine diseases

Since the discovery and structural elucidation of corticotropin-releasing factor (CRF) synthetic ovine and human CRF have become useful tools for the diagnosis of pituitary and adrenocortical disorders. The stimulation of release of adrenocorticotropic hormone (ACTH) after a dose of 100 micrograms CRF allows differentiation of the various causes of secondary adrenal insufficiency. In patients with specific autoimmune corticotroph disorders or general inflammatory or tumorous destruction of the anterior pituitary there is no rise of ACTH after intravenous administration of CRF. In contrast, patients with secondary adrenal failure due to suprasellar lesions show a rise of ACTH from a low or unmeasurable basal level without an accompanying cortisol response, demonstrating the integrity of the corticotroph and the atrophy of the cRF neuron and the adrenocortical cell. Similar observations are made in patients with secondary adrenal failure resulting from long-term glucocorticoid treatment. This demonstrates that the main reason for adrenal insufficiency after glucocorticoid treatment is the persisting suppression of the activity of CRF neurons. In patients with adrenocortical hyperfunction (Cushing's syndrome) the CRF stimulation test differentiates unequivocally between autonomous adrenal hypercortisolism and ACTH-dependent bilateral adrenal hyperplasia. However, the differential diagnosis between eutopic pituitary (Cushing's disease) and paraneoplastic ACTH secretion (ectopic ACTH syndrome) is difficult. Recent results show that catheterization of the sinus petrous inferior and measurement of ACTH in central and peripheral blood before and after CRF injection allows this differential diagnosis to be made with confidence. The usefulness of measuring CRF plasma levels is not established. The only exception to this is in cases of ectopic CRF syndrome, which is a rare cause of Cushing's syndrome.

Cortical seeding of a craniopharyngioma after craniotomy: case report

BACKGROUND

Cortical seeding of a craniopharyngioma has been rarely reported. We present a case that ectopically recurred along the tract of a previous surgical route.

METHODS

A 27-year-old woman presented earlier with a suprasellar craniopharyngioma. A left frontotemporal craniotomy was done with subtotal resection of the tumor because it was strongly adhered to the optic chiasm. Histopathology confirmed the diagnosis of craniopharyngioma. Six months after, the patient presented with decreased visual acuity and diplopia. She was reoperated through the previous craniotomy with a total resection. One year after the second surgery, the patient presented with seizures that were difficult to control. Magnetic resonance imaging revealed a contrast-enhancing tumor with cystic and solid components on the left temporal lobe cortex. The primary tumor bed was intact. The patient was reoperated, and the temporal lobe tumor was totally removed. Histologic studies showed an adamantinomatous craniopharyngioma. The patient was free of neurologic abnormalities, and no new lesion was found in the magnetic resonance imaging performed 1 year after the last surgery.

CONCLUSIONS

Although craniopharyngiomas exhibit a benign histopathologic pattern, a total resection combined with careful inspection and irrigation of the surgical field is the optimal treatment for preventing local and ectopic recurrences. It is strongly recommended that the concerned patients have a long-term clinical and neuroimaging follow-up.

Mechanisms of disease: The pathogenesis of pituitary tumors

Pituitary tumors exhibit a spectrum of biology, with variable growth and hormonal behaviors. They therefore provide an opportunity to examine pathogenetic mechanisms that underlie the neoplastic process. These include alterations in hormone regulation, growth-factor stimulation, cell-cycle control and cell-stromal interactions that result from genetic mutations or epigenetic disruption of gene expression. Mouse models have validated the roles of these alterations, which can be targets for the development of therapies that can manage these lesions. These therapies are increasingly recognized as critical for quality of life.

The role of hormones, growth factors and their receptors in pituitary tumorigenesis

Numerous factors have been shown to govern adenohypophysial cell proliferation. Human and animal models have documented that the hypothalamic trophic hormone growth hormone-releasing hormone stimulates cell proliferation, and prolonged stimulation leads to tumor formation. Similarly, lack of dopaminergic inhibition of lactotrophs and lack of feedback suppression by adrenal, gonadal or thyroid hormones are implicated, perhaps through hypothalamic stimulatory mechanisms, in pituitary adenoma formation superimposed on hyperplasia. However, most pituitary tumors are not associated with underlying hyperplasia. Overexpression of growth factors and their receptors, such as EGF, TGFalpha, EGF-R and VEGF has been identified in pituitary adenomas, and reduction of follistatin expression has been implicated in gonadotroph adenomas. Aberrant expression of members of the FGF family, an FGF antisense gene and FGF receptors have all been described in pituitary adenomas. The clonal composition of pituitary adenomas attests to the molecular basis of pituitary tumorigenesis, however, the evidence suggests that these various hypophysiotropic hormones and growth factors likely play a role as promoters of tumor cell growth in genetically transformed cells.

[Pituitary tumorigenesis]

Pituitary adenomas, almost invariably adenomas, account for 10% to 15% of all intracranial neoplasms and are incidentally detected in up to 27% of non selected autopsies. They are morphologically classified as microadenomas (diameter < 1 cm) or macroadenomas, which can be enclosed, invasive and/or expansive. Functionally, they are classified as secreting adenomas (PRL, GH, ACTH, TSH, LH, and FSH, and those co-secreting two or more hormones), and clinically non secreting or "non functioning" tumors. Diagnosis is based on the hypersecretion phenotype (acromegaly, Cushing, etc), and on mass effect of macroadenomas leading to neurological disturbances, mainly visual complaints and headache. Pituitary tumorigenesis mechanisms include those of primary hypothalamic versus pituitary origin, the latter is supported by evidence of pituitary adenoma monoclonality, as well as the absence of hyperplastic tissue surrounding the surgically removed tumor, and the relative independence of tumor hypothalamic control. Nevertheless, a permissive role of the hypothalamus on tumor progression is also postulated. Several molecular mechanisms involved in pituitary tumorigenesis have been unraveled including oncogenes, tumor suppressor genes and growth factors involved in neoplastic development, and will be described in this review.

Increased pituitary volume in antipsychotic-free and antipsychotic-treated patients of the AEsop first-onset psychosis study

Subjects at their first psychotic episode show an enlarged volume of the pituitary gland, but whether this is due to hypothalamic-pituitary-adrenal (HPA) axis hyperactivity, or to stimulation of the prolactin-secreting cells by antipsychotic treatment, is unclear. We measured pituitary volume, using 1.5-mm, coronal, 1.5 T, high-resolution MRI images, in 78 patients at the first psychotic episode and 78 age- and gender-matched healthy controls. In all, 18 patients were antipsychotic-free (12 of these were antipsychotic-naïve), 26 were receiving atypical antipsychotics, and 33 were receiving typical antipsychotics. As hypothesized, patients had a larger pituitary volume than controls (+22%, p< 0.001). When divided by antipsychotic treatment, and compared to controls, the pituitary volume was 15% larger in antipsychotic-free patients (p=0.028), 17% larger in patients receiving atypicals (p=0.01), and 30% larger in patients receiving typicals (p<0.001). Patients receiving typicals not only had the largest pituitary volume compared to controls but also showed a trend for a larger pituitary volume compared to the other patients grouped together (+11%, p=0.08). When divided by diagnosis, and compared to controls, the pituitary volume was 24% larger in patients with schizophrenia/schizophreniform disorder (n=40, p<0.001), 19% larger in depressed patients (n=13, p=0.022), 16% larger in bipolar patients (n=16, p=0.037), and 12% larger in those with other psychoses (n=9, p=0.2). In conclusion, the first-episode of a psychotic disorder is associated with a larger pituitary independently of the presence of antipsychotic treatment, and this could be due to activation of the HPA axis. Typical antipsychotics exert an additional enlarging effect on pituitary volume, likely to be related to activation of prolactin-secreting cells. This activation of the hormonal stress response could participate to the important metabolic abnormalities observed in patients with psychosis.

Pituitary surgery and postoperative management in Cushing's disease

Transsphenoidal pituitary surgery is the therapy for most Cushing's disease patients. This article describes the surgical technique, efficacy, perioperative management, and complications associated with this procedure. Numerous biochemical tests of cortisol status have been studied for the evaluation of the postoperative patient. Factors that predict postoperative remission and future relapse of Cushing's disease are addressed. Secondary interventions for persistent or recurrent disease include repeat transsphenoidal resection, pituitary radiation, medical therapy, and bilateral adrenalectomy

[Adrenocortical secretory tumors]

Adrenocortical tumors are rare and mostly non-secreting; their discovery is incidental. When secreting, they produce steroid excess and result in a clinical presentation such as the Cushing syndrome, primary aldosteronism, virilization or feminization syndrome. Such tumors are mostly sporadic but can belong to hereditary syndromes predisposing to tumors. The diagnosis of secreting adrenocortical tumors is based upon clinical presentation and biological data associated with specific biological assessments. Adrenal imaging has been considerably improved with the development of CT scan, which can be completed by MRI if necessary. Most of adrenocortical tumors are adenoma, nevertheless some of them can be malignant and the prognosis of such carcinomas is poor. Management of secreting adrenocortical tumors requires surgery in most of the cases and laparoscopic access is now widely used and provides good results in the treatment of benign tumors.

Cushing's syndrome due to ectopic production of corticotropin-releasing hormone in an infant with ganglioneuroblastoma

OBJECTIVE

To report the first recognized case of Cushing's syndrome due to a corticotropin-releasing hormone (CRH)-secreting ganglioneuroblastoma, which was found in an 18-month-old boy with hypertensive encephalopathy.

METHODS

The clinical, biochemical, and immunohistochemical characteristics of this rare syndrome are described, and the relevant literature is reviewed.

RESULTS

An 18-month-old boy with a history of recent weight gain was admitted because of sudden onset of right fixed esotropia and left facial palsy after episodes of emesis. Magnetic resonance imaging showed old left frontal lobe and right hypothalamic infarcts. The patient had generalized obesity, decelerated linear growth, hypertrichosis, hypertension (144/103 mm Hg), hypokalemia, and proteinuria. The 24-hour urinary excretion of free cortisol, catecholamines, and metanephrines was increased. The serum cortisol concentration after a 1-mg overnight dexamethasone suppression test (DST) was 53.7 mg/dL (normal, <5). The serum adrenocorticotropic hormone (ACTH) concentration was 7 pg/mL (normal, 10 to 60), and the CRH level was 439 pg/mL (normal, 24 to 40). An overnight high-dose DST (8 mg) failed to suppress serum cortisol; however, both cortisol and ACTH were responsive to ovine CRH stimulation. Despite discordant dynamic endocrine testing and negative somatostatin receptor scintigraphy, computed tomography showed a right 3.6- by 3.0-cm extra-adrenal retroperitoneal mass with central calcification extending 7 cm cephalocaudally. The patient underwent exploratory laparotomy, followed by chemotherapy. Findings on light microscopic and immunohistochemical examination of the retroperitoneal mass were consistent with a ganglioneuroblastoma that expressed CRH, pro-opiomelanocortin, and ACTH.

CONCLUSION

The evaluation of Cushing's syndrome is one of the most complex endocrine challenges. In this case, it was due to ectopic production of CRH by a ganglioneuroblastoma. Because most CRH-producing tumors also secrete ACTH, the ectopic production may represent a paracrine phenomenon in addition to an endocrine phenomenon. The ectopic CRH may also indirectly provoke pituitary ACTH secretion. This dual mechanism may explain the resistance of the tumor to feedback inhibition and a CRH-stimulation response indistinguishable from that observed in pituitary-dependent Cushing's syndrome.

Mechanisms for pituitary tumorigenesis: the plastic pituitary

The anterior pituitary gland integrates the repertoire of hormonal signals controlling thyroid, adrenal, reproductive, and growth functions. The gland responds to complex central and peripheral signals by trophic hormone secretion and by undergoing reversible plastic changes in cell growth leading to hyperplasia, involution, or benign adenomas arising from functional pituitary cells. Discussed herein are the mechanisms underlying hereditary pituitary hypoplasia, reversible pituitary hyperplasia, excess hormone production, and tumor initiation and promotion associated with normal and abnormal pituitary differentiation in health and disease.

The Nelson's syndrome... revisited

Adrenalectomy is a radical therapeutic approach to control hypercortisolism in some patients with Cushing's disease. However it may be complicated by the Nelson's syndrome, defined by the association of a pituitary macroadenoma and high ACTH secretion after adrenalectomy. This definition has not changed since the end of the fifties. Today the Nelson's syndrome must be revisited with new to criteria using more sensitive diagnostic tools, especially the pituitary magnetic resonance imaging. In this paper we will review the pathophysiological aspects of corticotroph tumor growth, with reference to the impact of adrenalectomy. The main epidemiological data on the Nelson's syndrome will be presented. More importantly, we will propose a new pathophysiological and practical approach to this question which attempts to evaluate the Corticotroph Tumor Progression after adrenalectomy, rather than to diagnose the Nelson's syndrome. We will discuss the consequences for the management of Cushing's disease patients after adrenalectomy, and will also draw some perspectives.

Targeted overexpression of luteinizing hormone causes ovary-dependent functional adenomas restricted to cells of the Pit-1 lineage

The majority of pituitary adenomas in humans are nonmetastasizing, monoclonal neoplasms that occur in approximately 20% of the general population. Their development has been linked to a combination of extrinsic factors and intrinsic defects. We now demonstrate with transgenic mice that targeted and chronic overexpression of LH causes ovarian hyperstimulation and subsequent hyperproliferation of Pit-1-positive cells that culminates in the appearance of functional pituitary adenomas ranging from focal to multifocal expansion of lactotropes, somatotropes, and thyrotropes. Tumors fail to develop in ovariectomized mice, indicating that contributions from the ovary are necessary for adenoma development. Although the link between chronic ovarian hyperstimulation and PRL-secreting adenomas was expected, the involvement of somatotropes and thyrotropes was surprising and suggests that multiple ovarian hormones may contribute to this unusual pathological consequence. In support of this idea, we have found that ovariectomy followed by estrogen replacement results in the expansion of lactotropes selectively in LH overexpressing mice, but not somatotropes and thyrotropes. Collectively, these data indicate that estrogen is sufficient for the formation of lactotrope adenomas only in animals with a hyperstimulated ovary, whereas the appearance of GH- and TSH-secreting adenomas depends on multiple ovarian hormones. Together, our data expand current models of pituitary tumorigenesis by suggesting that chronic ovarian hyperstimulation may underlie the formation of a subset of pituitary adenomas containing lactotropes, somatotropes, and thyrotropes.

Molecular defects in the pathogenesis of pituitary tumours

The majority of pituitary adenomas are trophically stable and change relatively little in size over many years. A comparatively small proportion behave more aggressively and come to clinical attention through inappropriate hormone secretion or adverse effects on surrounding structures. True malignant behaviour with metastatic spread is very atypical. Pituitary adenomas that come to surgery are predominantly monoclonal in origin and roughly half are aneuploid, indicating either ongoing genetic instability or transition through a period of genetic instability at some time during their development. Few are associated with the classical mechanisms of tumour formation but it is generally believed that the majority harbour quantitative if not qualitative differences in molecular composition compared to the normal pituitary. Despite their prevalence and the ready availability of biopsy material, at the present time, the precise molecular pathogenesis of the majority of pituitary adenomas remains unclear. This review summarizes current thinking.