Pharmacologic Management of Cushing Syndrome

Neurochemical Anatomy of Cushing's Syndrome

The neurochemical anatomy underlying Cushing's syndrome is examined for regional brain metabolism as well as neurotransmitter levels and receptor binding of biogenic amines and amino acids. Preliminary studies generally indicate that glucose uptake, blood flow, and activation on fMRI scans decreased in neocortical areas and increased in subcortical areas of patients with Cushing's syndrome or disease. Glucocorticoid-mediated increases in hippocampal metabolism occurred despite in vitro evidence of glucocorticoid-induced decreases in glucose uptake or consumption, indicating that in vivo increases are the result of indirect, compensatory, or preliminary responses. In animal studies, glucocorticoid administration decreased 5HT levels and 5HT1A receptor binding in several brain regions while adrenalectomy increased such binding. Region-specific effects were also obtained in regard to the dopaminergic system, with predominant actions of glucocorticoid-induced potentiation of reuptake blockers and releasing agents. More in-depth neuroanatomical analyses are warranted of these and amino acid-related neurotransmission.

Characterization of persistent and recurrent Cushing's disease

A case of possible recurrent Cushing's disease (CD) is presented and data on current definitions of CD remission, persistence, and recurrence are reviewed. While prevailing guidelines recommend the use of serum cortisol in the first post-operative week for defining initial remission and predicting sustained remission, with the use of 24 h urinary free cortisol measurements if serum cortisol values are equivocal, there is debate as to which methods and thresholds best define CD remission and predict successful outcomes. Other methods used to define remission (and hence persistence and recurrence) include restoration of cortisol suppression after dexamethasone and physiologic diurnal cortisol rhythm as measured by midnight salivary free cortisol. However, the number and degree of abnormal test results needed to define recurrence, and the determination of which biochemical test has more significance when there are discrepancies between markers is inconsistent among studies. Further inquiry is warranted to examine if patients in apparent CD remission who have subtle hypothalamic pituitary adrenal (HPA) axis abnormalities represent distinctive remission subtypes versus mild or early recurrence. Additional investigation could also explore the degree to which these HPA axis abnormalities, such as alterations in cortisol circadian rhythm or partial resistance to dexamethasone, are associated with persistence of CD morbidities, including neuropsychiatric impairments, alterations in body composition, and cardiovascular risk.

Ursolic acid suppresses growth and adrenocorticotrophic hormone secretion in AtT20 cells as a potential agent targeting adrenocorticotrophic hormone-producing pituitary adenoma

Adrenocorticotrophic hormone (ACTH)-producing pituitary adenoma leads to excess ACTH secretion, which is associated with significant mortality and impaired quality of life. Thus far, the first line therapy is the transphenoidal microsurgery. Considering the high recurrence rate and complications of surgery, novel agents, which directly target on pituitary ACTH-producing adenoma and suppress ACTH secretion are urgently required. In the present study, the effect of ursolic acid (UA) as a candidate agent targeting ACTH-producing AtT20 cells was investigated. It was demonstrated that UA inhibited the viability and induced apoptosis of AtT20 cells and decreased ACTH secretion. The process of apoptosis involved a decrease of the B cell lymphoma 2 (Bcl-2)/Bcl2-associated X protein ratio followed by a release of mitochondrial cytochrome c into the cytosol with subsequent activation of caspase-9, -3/7 and -8. The potential signaling pathway involved the activation of c-Jun N-terminal kinase (JNK) but not extracellular signal-regulated protein kinases1/2 and p38 mitogen-activated protein kinase. The JNK pathway participated in UA-induced mitochondrial apoptotic signaling transduction via increasing the phosphorylation and degradation of Bcl-2, which may be partly attenuated by the JNK inhibitor SP600125. In conclusion, the present study indicates that UA may be a promising candidate agent for the management of ACTH-producing pituitary adenoma.

Regulation of corticosterone secretion is modified by PFOS exposure at different levels of the hypothalamic-pituitary-adrenal axis in adult male rats

Perfluorooctane sulfonate (PFOS) is a fluorinated compound and a Persistent Organic Pollutant which can disrupt the endocrine system. This work was undertaken to evaluate the possible effects of PFOS exposure on the regulation of corticosterone secretion in adrenal and pituitary glands and at hypothalamic level in adult male rat, and to evaluate the possible morphological alterations induced by PFOS in this endocrine tissue. Adult male rats were orally treated with 0.5, 1.0, 3.0 and 6.0 mg of PFOS/kg/day for 28 days. Corticosterone, adrenocorticotropic hormone (ACTH) and corticotrophin-releasing hormone (CRH) secretion decreased in PFOS-treated rats. After PFOS exposure, relative expression of adrenocorticotropic hormone receptor (ACTHr) and proopiomelanocortin (POMC) genes was increased in adrenal and in pituitary glands, respectively; while relative expression of ACTHr and CRH genes decreased in hypothalamus with the doses of 0.5 and 1.0 mg/kg/day. PFOS treatment increased relative nitric oxide synthase 1 and 2 (NOS1 and NOS2) gene expression in the adrenal gland, and incremented superoxide dismutase activity. PFOS exposure induces a global inhibition of the hypothalamic-pituitary-adrenal (HPA) axis activity, and small morphological changes were observed in adrenal zona fasciculata cells.

[Vasopressin receptor antagonists: the vaptans]

The non-peptide vasopressin antagonists (VPA), called vaptans, were developed in the 1990s to antagonize both the pressor and antidiuretic effects of vasopressin. There are three subtypes of VPA receptors: V1a, V1b and V2. V1a receptors are widely distributed in the body, mainly the blood vessels and myocardium. The V1b receptors are located mainly in the anterior pituitary gland and play a role in ACTH release. V2 receptors are located in the collecting tubular renal cells. Both V1a and V1b receptors act through the intracellular phosphoinositol signalling pathway, Ca(++) being the second messenger. V2 receptors work through AMPc generation, which promotes aquaporin 2 (AQP2) trafficking and allows water to enter the cell. The vaptans act competitively at the AVP receptor. The most important are mozavaptan, lixivaptan, satavaptan and tolvaptan, all of which are selective V2 antagonists and are administered through the oral route. In contrast, conivaptan is a dual V1 and V2 antagonist administered through the endovenous route. The main characteristics of vaptans are their effect on free water elimination without affecting electrolyte excretion. There are several studies on the effects of these drugs in hypervolemic hyponatremia (heart failure, hepatic cirrhosis) as well as in normovolemic hyponatremia (inappropriate secretion of ADH [SIADH]). Current studies show that the vaptans are effective and well tolerated, although knowledge of these drugs remains limited. There are no studies of the use of vaptans in severe hyponatremia. Osmotic demyelination syndrome due to excessively rapid correction of hyponatremia has not been described.

Peri-operative management of Cushing's disease

Management of patients with ACTH producing pituitary adenoma remains to be challenging. Removal of the pituitary adenoma through transsphenoidal surgery is the main stay of treatment. Complete resection of the adenoma is followed by the development of ACTH deficiency since the normal corticotrophs are suppressed by the pre-existing hypercortisolemia. The concern for ACTH deficiency has led many centers to advocate the use glucocorticoids before, during and after surgery. We provide evidence that such coverage with glucocorticoids is unnecessary until clinical or biochemical documentation of need is established. Given that patients are closely monitored, they are immediately treated with glucocorticoids once they exhibit any clinical and/or biochemical evidence of adrenal insufficiency. Defining remission in the immediate postoperative period has been rather difficult despite using different biochemical markers. Serum cortisol continues to be the best determinant of disease activity after surgical adenomectomy. However it needs to be interpreted with caution as a biochemical marker of remission in patients given glucocorticoids during and after surgery. Other biochemical markers are also used in the peri-operative period to determine the possibility of remission. These include the dexamethasone suppression test, CRH stimulation without dexamethasone, urinary free cortisol measurements, desmopressin stimulation test, the determination of salivary cortisol and / or plasma ACTH concentrations. Each test has its own advantages and limitations. The simplest and most informative approach is to measure serum cortisol levels repeatedly after surgery without the administration of exogenous glucocorticoids. Low serum cortisol levels (less than 2 μg/dL) in the peri-operative period are highly indicative of surgical success and a high likelihood for clinical remission. Higher serum cortisol levels require careful interpretation and further planning and discussions between the patient and the management team.

Clinical features and management of ectopic ACTH syndrome at a single institute in Japan

Ectopic ACTH syndrome (EAS) is a diagnostic challenge because it is often indistinguishable from Cushing's disease. We describe our series of EAS patients referred to us during 1992-2009. Among 16 cases (9 females / 7 males), with mean age of 58.4 ± 19.0yr, the ectopic source was identified in ten (proven EAS), whereas unidentified in six (occult/unknown EAS). Their salient clinical manifestations included Cushingoid feature (88%), skin pigmentation (88%), profound hypokalemia (88%), hypertension (75%), diabetes/impaired glucose tolerance (75%), hyperlipidemia (69%), and severe infection (44%). Dynamic endocrine tests revealed markedly elevated plasma ACTH levels (211 ± 116pg/mL) and cortisol levels (60.9 ± 30.1µg/dL) which showed resistance to overnight high-dose (8mg) dexamethasone suppression test in 15 (94%) and unresponsiveness to CRH stimulation in 12 (75%). No ACTH gradient during inferior petrosal sampling was noted in 13 of 15 (87%). Imaging tests by CT/MRI identified the tumors in 8 of 16 (50%), in 4 of 11 (36%) and 4 of 6 (66.7%) octreotide-responders by somatostatin receptor scintigraphy, but in only one of 9 (11.1%) by FDG-PET scan. Six cases deceased, including small cell carcinoma (2) and adenocarcinoma (1) of lung, neuroendocrine carcinoma of pancreas (1) and stomach (1), and olfactory neuroblastoma (1), whereas 4 cases survived after removal of the tumors, including bronchial carcinoid tumor (3) and thymic hyperplasia (1). Six occult/unknown EAS patients survived for 67.5 months after medical treatment with metyrapone to control hypercortisolism. Thus, various endocrine tests combined with imaging studies are required to correctly localize the tumors. Control of hypercortisolemia by metyrapone, even if tumor is unrecognized, is critical for better prognosis, and the long-term follow-up by repeated endocrine and imaging tests is mandatory.

Should we evaluate for cardiovascular disease in patients with Cushing's syndrome?

Current evidence indicates a strong association between Cushing's syndrome, characterized by a cluster of systemic complications and increased cardiovascular risk. The biological link is cortisol overproduction, which influences various pathogenetic processes leading to cardiovascular damage, a main cause of increased mortality. Anthropometric and biochemical profile (including fasting glucose, lipids, potassium and coagulation parameters), clinical blood pressure measurement and electrocardiogram should be routinely carried out. Oral glucose tolerance test, 24-h ambulatory blood pressure monitoring, echocardiography and carotid ultrasound are recommended for further evaluation. Search for cardiac and vascular damage, according to specialist's advice, is mandatory in complicated hypertension or diabetes, as part of a comprehensive assessment. A combination of treatments directed against the aetiology of hypercortisolism and aimed at controlling cardiovascular risk factors, is required in this complex condition.

Cyclic Cushing's syndrome: an overview

Cyclic Cushing's syndrome (CS) is a disorder in which glucocorticoid levels are alternately normal and high, the latter occurring in episodes that can last from a few days to several months. It is more common in children than in adults. Cyclic CS may be either of the two different forms of CS (ACTH-dependent or -independent CS). Clinically, it may present with one or many symptoms, depending on the duration of disease activity and the timing of the fluctuations. A serotoninergic influence, cyclic changes in central dopaminergic tone, spontaneous episodic hemorrhage in the tumor, and the action of inflammatory cytokines with antitumor properties are some of the mechanisms suggested to explain the physiopathology of this phenomenon but the exact mechanism remains to be clarified. The cyclic pattern of hypercortisolism can delay the final diagnosis of CS and make it difficult to interpret the results of dynamic tests. Patients may have paradoxical responses to dexamethasone that can reflect increasing or decreasing levels of endogenous activity. Hormone assessments have to be repeated periodically when a diagnosis of CS is suspected. The cyclic pattern can also interfere with medical treatment because patients may show unexpected clinical and biochemical signs of hypocortisolism when cortisol secretion cyclically returns to normal, so an accurate follow-up is mandatory in these patients.

Treatment of adrenocorticotropin-dependent Cushing's syndrome: a consensus statement

OBJECTIVE

Our objective was to evaluate the published literature and reach a consensus on the treatment of patients with ACTH-dependent Cushing's syndrome, because there is no recent consensus on the management of this rare disorder.

PARTICIPANTS

Thirty-two leading endocrinologists, clinicians, and neurosurgeons with specific expertise in the management of ACTH-dependent Cushing's syndrome representing nine countries were chosen to address 1) criteria for cure and remission of this disorder, 2) surgical treatment of Cushing's disease, 3) therapeutic options in the event of persistent disease after transsphenoidal surgery, 4) medical therapy of Cushing's disease, and 5) management of ectopic ACTH syndrome, Nelson's syndrome, and special patient populations.

EVIDENCE

Participants presented published scientific data, which formed the basis of the recommendations. Opinion shared by a majority of experts was used where strong evidence was lacking.

CONSENSUS PROCESS

Participants met for 2 d, during which there were four chaired sessions of presentations, followed by general discussion where a consensus was reached. The consensus statement was prepared by a steering committee and was then reviewed by all authors, with suggestions incorporated if agreed upon by the majority.

CONCLUSIONS

ACTH-dependent Cushing's syndrome is a heterogeneous disorder requiring a multidisciplinary and individualized approach to patient management. Generally, the treatment of choice for ACTH-dependent Cushing's syndrome is curative surgery with selective pituitary or ectopic corticotroph tumor resection. Second-line treatments include more radical surgery, radiation therapy (for Cushing's disease), medical therapy, and bilateral adrenalectomy. Because of the significant morbidity of Cushing's syndrome, early diagnosis and prompt therapy are warranted.

Non-peptide arginine-vasopressin antagonists: the vaptans

Arginine-vasopressin is a hormone that plays an important part in circulatory and water homoeostasis. The three arginine-vasopressin-receptor subtypes--V1a, V1b, and V2--all belong to the large rhodopsin-like G-protein-coupled receptor family. The vaptans are orally and intravenously active non-peptide vasopressin receptor antagonists that are in development. Relcovaptan is a selective V1a-receptor antagonist, which has shown initial positive results in the treatment of Raynaud's disease, dysmenorrhoea, and tocolysis. SSR-149415 is a selective V1b-receptor antagonist, which could have beneficial effects in the treatment of psychiatric disorders. V2-receptor antagonists--mozavaptan, lixivaptan, satavaptan, and tolvaptan--induce a highly hypotonic diuresis without substantially affecting the excretion of electrolytes (by contrast with the effects of diuretics). These drugs are all effective in the treatment of euvolaemic and hypervolaemic hyponatraemia. Conivaptan is a V1a/V2 non-selective vasopressin-receptor antagonist that has been approved by the US Food and Drug Administration as an intravenous infusion for the inhospital treatment of euvolaemic or hypervolaemic hyponatraemia.

Autopsy of a patient with Cushing's Syndrome who was revealed to have pulmonary tumorlets producing ectopic ACTH

The patient, a 78-year-old female with a 10-year history of type 2 diabetes mellitus, was admitted to our department for evaluation of leg edema and general fatigue. Biochemical investigations revealed hypokalemia and elevated serum cortisol and plasma ACTH levels, with a loss of diurnal rhythm and failure of suppression at high doses (8 mg) of dexamethasone. No pituitary tumor or parasellar tumor was detected by contrast-enhanced computed tomography (CT) or magnetic resonance image scan of the pituitary. High resolution CT of the lung and bronchoscopic examination revealed no abnormalities. Abdominal and pelvic CT indicated bilateral, slightly diffuse, adrenal gland hyperplasia only. These findings led to a diagnosis of ACTH-dependent hypercortisolism from an undefined source. Ten days after admission the patient had a fever and was diagnosed with disseminated intravascular coagulation. Despite intensive treatment about 1 month after admission the patient died from progressive multiple organ failure. At autopsy, a histological examination of the periphery of the right middle lobe of the lung revealed the presence of tumorlets. Immunohistochemical staining of the tumorlets revealed scattered cells containing ACTH and many cells containing chromogranin A that were positive for Grimelius staining. In addition, multiple microabscesses were present throughout most tissues of the body. The ectopic hormonal production observed in the present case suggests that pulmonary tumorlets should thus be considered in the differential diagnosis of Cushing's syndrome, and medical treatment to inhibit steroidogenesis should be started immediately to reduce the risk of complications from hypercortisolism.

Advances in medical treatment of Cushing's disease

It is well known that transphenoidal surgery is the first line of treatment for Cushing's disease (CD). In case of recurrence, pituitary irradiation or adrenalectomy are usually performed; however, the morbidity due to these procedures is not negligible. For this reason, there is still a strong need for medical therapy, although there are only a few controlled data on this field. A variety of compounds are invaluable complementary tools in the management of this serious condition for which no treatment has yet been proven fully satisfactory. Pharmacological treatment could be employed by using neuromodulatory drugs (i.e., serotonin antagonists, dopamine, and GABA agonists) active only in a few cases of hypothalamic-pituitary-dependent CD. New approaches at the pituitary tumor level involve the potential use of other compounds (e.g., PPAR-γ agonists and retinoic acid). Exciting news in treating CD includes the recent availability of new multiligand somatostatin analogues. This review focuses on the new potential pharmacologic approaches for the management of CD based on the recent identification of possible targets and/or pathogenetic mechanisms.

Cushing disease: use of perioperative serum cortisol measurements in early determination of success following pituitary surgery

✓Despite many recent advances, management of cases of Cushing disease continues to be challenging. After complete resection of ACTH-secreting adenomas, patients develop transient ACTH deficiency requiring glucocorticoid replacement for several months. The current recommendation by many centers, including ours, for patients with ACTH-secreting adenomas is to withhold glucocorticoid therapy during and immediately after adenomectomy until there is clinical or biochemical evidence of ACTH deficiency. A serum cortisol level of less than 2 μg/dl within the first 48 hours after adenomectomy is a reliable biochemical marker of ACTH deficiency and is associated with clinical remission of Cushing disease. Higher serum cortisol levels in the immediate postoperative period should be interpreted with caution. The decision to immediately reexplore the sella turcica should be individualized, taking into account the findings at surgery, the histopathological findings, and the changes in serum cortisol levels as well as the patient's wishes and concerns. Optimal diagnosis and therapy for patients with Cushing disease require thorough and close coordination and involvement of all members of the management team.

Peroxisome proliferator-activated receptor gamma in the human pituitary gland: expression and splicing pattern in adenomas versus normal pituitary

Pituitary adenomas are slow-growing tumours arising within the pituitary gland. If secreting, they give rise to well-known syndromes such as Cushing's disease or acromegaly; when hormonally inactive, they come to clinical attention often with local mass effects or pituitary deficiency. Peroxisome proliferator-activated receptor gamma (PPARgamma), a nuclear hormone receptor with a key role in fat and glucose metabolism, but also involved in several neoplasia, has recently been detected in pituitary adenomas. In the present study, we evaluated the occurrence and splicing profile of PPARgamma in 43 cases of pituitary adenoma of different subtypes and compared it to 12 normal pituitary glands. By real-time polymerase chain reaction, PPARgamma was expressed as much in adrenocorticotrophic hormone (ACTH)-secreting and ACTH-silent adenomas as in controls, with a moderate underexpression in somatotrophinomas and prolactinomas and overexpression in 54% of nonfunctioning pituitary adenomas (NFPA). There was no apparent qualitative change in the splicing profile of pathological pituitary glands, nor was the presence of specific isoforms with dominant negative effects against PPARgamma detected. Western blotting revealed similar expression levels in the different subgroups of pituitary adenomas and normal glands. Immunohistochemistry confirmed PPARgamma expression in approximately one-half of analysed samples. The intra- and intergroup differences observed in pituitary adenomas may represent new elements in the process of understanding the different clinical responses of Cushing's and Nelson patients to PPARgamma-ligand treatment. Moreover, the higher level of PPARgamma expression detected in the NFPA subgroup may suggest its possible role as a molecular target in these pituitary adenomas, paving the way for investigations on the effectiveness of treatment with thiazolidinediones in such patients.

Adrenal toxicology: a strategy for assessment of functional toxicity to the adrenal cortex and steroidogenesis

The adrenal is the most common toxicological target organ in the endocrine system in vivo and yet it is neglected in regulatory endocrine disruption screening and testing. There has been a recent marked increase in interest in adrenal toxicity, but there are no standardised approaches for assessment. Consequently, a strategy is proposed to evaluate adrenocortical toxicity. Human adrenal conditions are reviewed and adrenocortical suppression, known to have been iatrogenically induced leading to Addisonian crisis and death, is identified as the toxicological hazard of most concern. The consequences of inhibition of key steroidogenic enzymes and the possible toxicological modulation of other adrenal conditions are also highlighted. The proposed strategy involves an in vivo rodent adrenal competency test based on ACTH challenge to specifically examine adrenocortical suppression. The H295R human adrenocortical carcinoma cell line is also proposed to identify molecular targets, and is useful for measuring steroids, enzymes or gene expression. Hypothalamo-pituitary-adrenal endocrinology relevant to rodent and human toxicology is reviewed (with an emphasis on multi-endocrine axis effects on the adrenal and also how the adrenal affects a variety of other hormones) and the endocrinology of the H295R cell line is also described. Chemicals known to induce adrenocortical toxicity are reviewed and over 60 examples of compounds and their confirmed steroidogenic targets are presented, with much of this work published very recently using H295R cell systems. In proposing a strategy for adrenocortical toxicity assessment, the outlined techniques will provide hazard assessment data but it will be regulatory agencies that must consider the significance of such data in risk extrapolation models. The cases of etomindate and aminoglutethimide induced adrenal suppression are clearly documented examples of iatrogenic adrenal toxicity in humans. Environmentally, sentinel species, such as fish, have also shown evidence of adrenal endocrine disruption attributed to exposure to chemicals. The extent of human sub-clinical adrenal effects from environmental chemical exposures is unknown, and the extent to which environmental chemicals may act as a contributory factor to human adrenal conditions following chronic low-level exposures will remain unknown unless purposefully studied.

Cushing's Syndrome: important issues in diagnosis and management

CONTEXT

The diagnosis, differential diagnosis, and treatment of Cushing's syndrome are challenging problems in clinical endocrinology. We focus on critical questions addressing screening for Cushing's syndrome, differentiation of Cushing's subtypes, and treatment options.

EVIDENCE ACQUISITION

Ovid's MEDLINE (1996 through April 2006) was used to search the general literature. We also relied on previously published reviews and a recent monograph and cite a mix of primary articles and recent reviews.

EVIDENCE SYNTHESIS

Although this article represents our opinion, it draws heavily on a recent consensus statement from experts in the field and a recent monograph on Cushing's syndrome.

CONCLUSIONS

We concluded that: 1) measurement of late-night or bedtime salivary cortisol is a useful approach to screen for Cushing's syndrome; 2) measurement of suppressed plasma ACTH by immunometric assay is useful to differentiate ACTH-dependent and -independent Cushing's syndrome; 3) inferior petrosal sinus sampling for ACTH should be performed in patients with ACTH-dependent hypercortisolism in whom a pituitary magnetic resonance imaging is normal or equivocal (in the absence of a pituitary ACTH gradient, prolactin levels should be measured to confirm the integrity of venous sampling); 4) computed tomography of the chest and abdomen and somatostatin receptor scintigraphy should be performed in patients with the occult ectopic ACTH syndrome; and 5) patients with Cushing's disease should be referred to a neurosurgeon with extensive experience operating on corticotroph microadenomas. Bilateral laparoscopic adrenalectomy should be considered in patients with Cushing's disease who fail therapies directed at the pituitary.