Profound amplification of secretory-burst mass and anomalous regularity of ACTH secretory process in patients with Nelson's syndrome compared with Cushing's disease

Two Distinctive POMC Promoters Modify Gene Expression in Cushing Disease

CONTEXT

Mechanisms underlying pituitary corticotroph adenoma adrenocorticotropin (ACTH) production are poorly understood, yet circulating ACTH levels closely correlate with adenoma phenotype and clinical outcomes.

OBJECTIVE

We characterized the 5' ends of proopiomelanocortin (POMC) gene transcripts, which encode the precursor polypeptide for ACTH, in order to investigate additional regulatory mechanisms of POMC gene transcription and ACTH production.

METHODS

We examined 11 normal human pituitary tissues, 32 ACTH-secreting tumors, as well as 6 silent corticotroph adenomas (SCAs) that immunostain for but do not secrete ACTH.

RESULTS

We identified a novel regulatory region located near the intron 2/exon 3 junction in the human POMC gene, which functions as a second promoter and an enhancer. In vitro experiments demonstrated that CREB binds the second promoter and regulates its transcriptional activity. The second promoter is highly methylated in SCAs, partially demethylated in normal pituitary tissue, and highly demethylated in pituitary and ectopic ACTH-secreting tumors. In contrast, the first promoter is demethylated in all POMC-expressing cells and is highly demethylated only in pituitary ACTH-secreting tumors harboring the ubiquitin-specific protease 8 (USP8) mutation. Demethylation patterns of the second promoter correlate with clinical phenotypes of Cushing disease.

CONCLUSION

We identified a second POMC promoter regulated by methylation status in ACTH-secreting pituitary tumors. Our findings open new avenues for elucidating subcellular regulation of the hypothalamic-pituitary-adrenal axis and suggest the second POMC promoter may be a target for therapeutic intervention to suppress excess ACTH production.

Cushing's syndrome - Disease monitoring: Recurrence, surveillance with biomarkers or imaging studies

Pituitary surgery is the first-line treatment for patients with Cushing's disease. For patients who are not considered candidates for pituitary surgery, pituitary radiation and bilateral adrenalectomy are further treatment alternatives. Not all patients are cured with pituitary surgery, and a substantial number of patients develop recurrence, sometimes many years after an apparently successful treatment. The same applies to patients treated with radiotherapy. Far from all patients are cured, and in many cases the disease recurs. Bilateral adrenalectomy, although always curative, causes chronic adrenal insufficiency and the remaining pituitary tumour can continue to grow and cause symptoms due to pressure on adjacent tissues, a phenomenon called Nelson's syndrome. In this paper the rate of recurrence of hypercortisolism, as well as the rate of development of Nelson's syndrome, following treatment of patients with Cushing's syndrome, will be reviewed. The aim of the paper is also to summarize clinical and biochemical factors that are associated with recurrence of hypercortisolism and how the patients should be monitored following treatment.

Bilateral adrenalectomy for Cushing's syndrome: Pros and cons

AIM

To assess the outcome of patients undergoing bilateral adrenalectomy for Cushing's syndrome (CS).

METHODS

All patients who underwent bilateral adrenalectomy for CS at the Department of Endocrine Surgery, Sanjay Gandhi Postgraduate Institute of Medical Sciences hospital between 1991 and 2013 were included. Medical records were reviewed to obtain patient characteristics and follow-up data.

RESULTS

Twenty-seven patients were studied. Mean age was 28.74 ± 12.95 years (range 9-60), male:female ratio was 1.7:1. About half that is, 48.19% were of Cushing's disease (failed trans-sphenoidal surgery [TSS]), 37.04% were of ectopic CS (ECS), and 14.81% were of CS due to bilateral adrenal pathology. Median follow-up period was 80.5 months. Before surgery, 74.1% patients had body mass index > which after surgery declined to <25 in 75% of them. Hypertension was present in 85.2% and after surgery resolved in 40%. Diabetes mellitus was present in 44.4% and after surgery resolved in 33% of them. Hirsutism and proximal muscle weakness were present in 55.6% and 70.4% patients, respectively, and after surgery improved markedly in all patients. Adrenal crisis developed in 36.3% and Nelson's syndrome in 41.7% patients during follow-up. Three patients died in perioperative period while three succumbed to the disease during follow-up. Two patients developed recurrence of endogenous cortisol production during the follow-up period.

CONCLUSIONS

Bilateral adrenalectomy is a valid treatment option for palliating severe symptoms in Pituitary Cushing's with failed TSS and unlocalized ECS but the procedure is curative for CS due to bilateral adrenal disease. Overall morbidity and mortality is higher than other endocrine operations. Co-morbidities tend to be more severe and are a risk factor for mortality during the time patient survives.

Re-examining Nelson's syndrome

PURPOSE OF REVIEW

Nelson's syndrome is a rare complication that can occur during the course of management of Cushing's disease. This article summarizes the recent literature on the diagnosis, monitoring and treatment of this potentially life-threatening outcome.

RECENT FINDINGS

Nelson's syndrome, with rising adrenocorticotropin hormone levels and corticotroph tumor progression on diagnostic imaging, can develop following treatment of refractory Cushing's disease with total bilateral adrenalectomy with/without radiotherapy. However, data showing that radiotherapy prevents Nelson's syndrome is inconsistent. In addition to the treatment of Nelson's syndrome with neurosurgery with/without adjuvant radiotherapy, selective somatostatin analogs and dopamine agonists, as well as other novel agents, have been used with increasing frequency in treating cases of Nelson's syndrome with limited benefit. The risk-benefit profile of each of these therapies is still not completely understood.

SUMMARY

Consensus guidelines on the evaluation and management of Nelson's syndrome are lacking. This article highlights areas in the surveillance of Cushing's disease patients, and diagnostic criteria and treatment regimens for Nelson's syndrome that require further research and review by experts in the field.

Impact of Adiposity and Fat Distribution on the Dynamics of Adrenocorticotropin and Cortisol Rhythms

Obesity impacts many hormonal systems, including pituitary hormones, as well as insulin and leptin. In this review we discuss articles which investigate the influence of obesity on the hypothalamic-pituitary-adrenal (HPA) axis. Different techniques have been used to assess the function of the HPA-axis in obesity, including measuring fasting and/or late evening levels of adrenocorticotropic hormone (ACTH) and (free) cortisol in plasma and saliva, studying feedback with dexamethasone or cortisol, and evaluating responsiveness of the system to corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP) or ACTH 1-29. In addition, more elaborate studies investigated 24-h secretion patterns, analyzed with deconvolution techniques to quantitate pulsatile secretion rates of cortisol and less often ACTH. Other investigators used timed infusions of labeled cortisol for the estimation of the 24-h secretion rate, clearance rate and distribution volume. Many studies relied on the 24-h urinary excretion of free cortisol, but for quantitation of the 24-h secretion, measurement of all cortisol-derived metabolites is required. Several studies have applied modern liquid chromatography-tandem-mass spectrometry techniques to measure these metabolites. The picture emerging from all these studies is that, first, ACTH secretion is amplified, likely via enhanced forward drive; and, second, serum cortisol levels are normal or even low, associated with a normal 24-h cortisol secretion per liter distribution volume determined by deconvolution, but enhanced when based on the increased total distribution volume associated with obesity. Increased cortisol secretion was also established by isotope dilution studies and reports based on the measurement of all urinary cortisol metabolites. The responsiveness of the adrenal gland to ACTH is diminished. The studies do not address quantitative aspects of cortisol-cortisone metabolism on individual organs, including liver, central and peripheral fat, intestine, skin, and muscle.

Thyrotropin secretion patterns in health and disease

Thyroid hormones are extremely important for metabolism, development, and growth during the lifetime. The hypothalamo-pituitary-thyroid axis is precisely regulated for these purposes. Much of our knowledge of this hormonal axis is derived from experiments in animals and mutations in man. This review examines the hypothalamo-pituitary-thyroid axis particularly in relation to the regulated 24-hour serum TSH concentration profiles in physiological and pathophysiological conditions, including obesity, primary hypothyroidism, pituitary diseases, psychiatric disorders, and selected neurological diseases. Diurnal TSH rhythms can be analyzed with novel and precise techniques, eg, operator-independent deconvolution and approximate entropy. These approaches provide indirect insight in the regulatory components in pathophysiological conditions.

Leksell Gamma Knife : An Effective Non Invasive Treatment for Rare Case of Nelson's Syndrome

Nelson's syndrome nowadays a rare entity results from an adrenocorticotropin (ACTH)-secreting pituitary adenoma in patients with refractory Cushing's disease after a therapeutic bilateral adrenal gland removal. We report a case of 25 year old female with cushing's disease who was initially managed with medical treatment, but in view of severe persistent hyper cortisol state was subjected to bilateral adrenalectomy following which she developed Nelson's syndrome after a gap of six years, which was difficult to diagnose because of limited investigations available. Patient was managed with stereotactic radiosurgery (gamma knife surgery).

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.

Pituitary-hormone secretion by thyrotropinomas

Hormone secretion by somatotropinomas, corticotropinomas and prolactinomas exhibits increased pulse frequency, basal and pulsatile secretion, accompanied by greater disorderliness. Increased concentrations of growth hormone (GH) or prolactin (PRL) are observed in about 30% of thyrotropinomas leading to acromegaly or disturbed sexual functions beyond thyrotropin (TSH)-induced hyperthyroidism. Regulation of non-TSH pituitary hormones in this context is not well understood. We there therefore evaluated TSH, GH and PRL secretion in 6 patients with up-to-date analytical and mathematical tools by 24-h blood sampling at 10-min intervals in a clinical research laboratory. The profiles were analyzed with a new deconvolution method, approximate entropy, cross-approximate entropy, cross-correlation and cosinor regression. TSH burst frequency and basal and pulsatile secretion were increased in patients compared with controls. TSH secretion patterns in patients were more irregular, but the diurnal rhythm was preserved at a higher mean with a 2.5 h phase delay. Although only one patient had clinical acromegaly, GH secretion and IGF-I levels were increased in two other patients and all three had a significant cross-correlation between the GH and TSH. PRL secretion was increased in one patient, but all patients had a significant cross-correlation with TSH and showed decreased PRL regularity. Cross-ApEn synchrony between TSH and GH did not differ between patients and controls, but TSH and PRL synchrony was reduced in patients. We conclude that TSH secretion by thyrotropinomas shares many characteristics of other pituitary hormone-secreting adenomas. In addition, abnormalities in GH and PRL secretion exist ranging from decreased (joint) regularity to overt hypersecretion, although not always clinically obvious, suggesting tumoral transformation of thyrotrope lineage cells.

Motivations and methods for analyzing pulsatile hormone secretion

Endocrine glands communicate with remote target cells via a mixture of continuous and intermittent signal exchange. Continuous signaling allows slowly varying control, whereas intermittency permits large rapid adjustments. The control systems that mediate such homeostatic corrections operate in a species-, gender-, age-, and context-selective fashion. Significant progress has been made in understanding mechanisms of adaptive interglandular signaling in vivo. Principal goals are to understand the physiological origins, significance, and mechanisms of pulsatile hormone secretion. Key analytical issues are: 1) to quantify the number, size, shape, and uniformity of pulses, nonpulsatile (basal) secretion, and elimination kinetics; 2) to evaluate regulation of the axis as a whole; and 3) to reconstruct dose-response interactions without disrupting hormone connections. This review will focus on the motivations driving and the methodologies used for such analyses.

Thyrotropin secretion by thyrotropinomas is characterized by increased pulse frequency, delayed diurnal rhythm, enhanced basal secretion, spikiness, and disorderliness

CONTEXT

Hormone secretion by somatotropinomas, corticotropinomas, and prolactinomas exhibits increased pulsatility and basal secretion, accompanied by greater disorderliness.

OBJECTIVE

Our objective was to evaluate TSH secretion by thyrotropinomas with up-to-date analytical and mathematical tools.

DESIGN

Twenty-four hour blood samplings at 10-min intervals in a clinical research laboratory in five patients with a thyrotropinoma and 10 healthy age- and gender-matched controls were performed. The obtained serum TSH profiles were analyzed with a new deconvolution method, approximate entropy, Cosinor analysis, and by quantification of spikiness.

RESULTS

TSH burst frequency and basal secretion were increased in patients compared with controls. TSH secretion patterns in patients were more irregular than in controls, but the diurnal rhythm was preserved at a higher mean in all patients, although with a 2-h phase delay.

CONCLUSION

TSH secretion by thyrotropinomas shares many characteristics with other pituitary hormone-secreting adenomas.

Nelson syndrome: comprehensive review of pathophysiology, diagnosis, and management

Nelson syndrome (NS) is a rare clinical manifestation of an enlarging pituitary adenoma that can occur following bilateral adrenal gland removal performed for the treatment of Cushing disease. It is characterized by excess adreno-corticotropin secretion and hyperpigmentation of the skin and mucus membranes. The authors present a comprehensive review of the pathophysiology, diagnosis, and management of NS. Corticotroph adenomas in NS remain challenging tumors that can lead to significant rates of morbidity and mortality. A better understanding of the natural history of NS, advances in neurophysiology and neuroimaging, and growing experience with surgical intervention and radiation have expanded the repertoire of treatments. Currently available treatments include surgical, radiation, and medical therapy. Although the primary treatment for each tumor type may vary, it is important to consider all of the available options and select the one that is most appropriate for the individual case, particularly in cases of lesions resistant to intervention.

Improved quality of life after bilateral laparoscopic adrenalectomy for Cushing's disease: a 10-year experience

OBJECTIVE

To determine long-term quality of life after bilateral adrenalectomy for persistent Cushing's disease after transsphenoidal pituitary tumor resection.

SUMMARY BACKGROUND DATA

Bilateral adrenalectomy for symptomatic relief of persistent hypercortisolism appears to be an effective treatment option. However, few studies have examined long-term outcomes in this patient population.

METHODS

Retrospective review of 39 patients treated by bilateral laparoscopic adrenalectomy for Cushing's disease from 1994 to 2004. Patients completed a follow-up phone survey, including our Cushing-specific questionnaire and the SF-12v2 health survey. Patients then refrained from taking their steroid replacement for 24 hours, and serum cortisol and ACTH levels were measured.

RESULTS

Three patients died at 12, 19, and 50 months following surgery from causes unrelated to adrenalectomy. The remaining 36 patients all responded to the study questionnaire (100% response rate). Patients were between 3 months and 10 years post-adrenalectomy. We had zero operative mortalities and a 10.3% morbidity rate. Our incidence of Nelson's syndrome requiring clinical intervention was 8.3%; 89% of patients reported an improvement in their Cushing-related symptoms, and 91.7% would undergo the same treatment again. Twenty of 36 (55%) and 29 of 36 (81%) patients fell within the top two thirds of the national average for physical and mental composite scores, respectively, on the SF-12v2 survey. An undetectable serum cortisol level was found in 79.4% of patients.

CONCLUSIONS

Laparoscopic bilateral adrenalectomy for symptomatic Cushing's disease is a safe and effective treatment option. The majority of patients experience considerable improvement in their Cushing's disease symptoms, and their quality of life equals that of patients initially cured by transsphenoidal pituitary tumor resection.

Nelson’s syndrome after bilateral adrenalectomy for Cushing’s disease

BACKGROUND

Presentation and outcome of Nelson's syndrome after bilateral adrenalectomy is variable.

METHODS

Clinical records of 39 patients who underwent bilateral adrenalectomy for primary or recurrent Cushing's disease during a 15-year period were analyzed for frequency and evolution of Nelson's syndrome.

RESULTS

The study included 32 females and 7 males with a mean age of 31 years; 20 patients had a hypophysectomy as the initial procedure, and 19 had an adrenalectomy. Of the group, 17 patients received prophylactic radiation therapy to the pituitary gland. A total of 11 patients, none of whom had received prophylactic radiation therapy, developed Nelson's syndrome (determined by skin hyperpigmentation, elevated serum ACTH levels, and enlargement of a previous pituitary tumor or development of a new tumor in patients with no previous pituitary abnormality) over a mean follow-up period of 53 months. Treatment for Nelson's syndrome included valproic acid, radiation therapy, and hypophysectomy as monotherapy or combined therapy. Of the remaining 28 patients, 10 (7 without prophylactic radio therapy) developed skin hyperpigmentation and increased ACTH levels without a tumor.

CONCLUSIONS

Nelson's syndrome is a frequent complication after bilateral adrenalectomy in the absence of prophylactic radiotherapy (28%). The syndrome can be successfully controlled by medical treatment and or radiotherapy; patients rarely require hypophysectomy.