Gene expression profiling in human corticotroph tumours reveals distinct, neuroendocrine profiles.

Adrenocorticotrophic hormone (ACTH)-secreting pituitary adenomas give rise to a severe endocrinological disorder, comprising Cushing's disease, with multifaceted clinical presentation and treatment outcomes. Experimental studies suggest that the disease variability is inherent to the pituitary tumour, thus indicating the need for further studies into tumour biology. The present study evaluated transcriptome expression pattern in a large series of ACTH-secreting pituitary adenoma specimens in order to identify molecular signatures of these tumours. Gene expression profiling of formalin-fixed, paraffin-embedded specimens from 40 human ACTH-secreting pituitary adenomas revealed the significant expression of genes involved in protein biosynthesis and ribosomal function, in keeping with the neuroendocrine cell profile. Unsupervised cluster analysis identified 3 distinct gene profile clusters and several genes were uniquely overexpressed in a given cluster, accounting for different molecular signatures. Of note, gene expression profiles were associated with clinical features, such as the age and size of the tumour. Altogether, the findings of the present study show that corticotroph tumours are characterised by a neuroendocrine gene expression profile and present subgroup-specific molecular features.

Role of the ubiquitin/proteasome system on ACTH turnover in rat corticotropes.

PURPOSE: A large number of studies has investigated proopiomelanocortin processing in anterior pituitary corticotropes but little is known on proopiomelanocortin/ACTH degradation within these cells. The ubiquitin-proteasome system is an intracellular protein degradation pathway which has garnered considerable interest in recent times, given its role in maintenance of protein homeostasis. Aim of the present study was to evaluate the role of the ubiquitin-proteasome system in proopiomelanocortin/ACTH turnover in pituitary corticotropes. METHODS: Rat anterior pituitary primary cultures were treated with 0.01-100 nM MG132, a proteasome inhibitor, or 0.1-100 nM K48R, an inhibitor of polyubiquitylation, for 4 and 24 h and ACTH concentrations in medium and cell lysates estimated by immunometric assay. Co-immunoprecipitation for ubiquitin and ACTH was carried out to establish ubiquitin-tagged protein products. RESULTS: Inhibition of proteasome-mediated degradation with MG132 lead to an increase in ACTH concentrations, both as regards secretion and cell content. Likewise, inhibition of polyubiquitylation was associated with increased ACTH secretion and cell content. Ubiquitin/ACTH co-immunoprecipitation revealed that proopiomelanocortin was a target of ubiquitylation. CONCLUSIONS: We provide the first evidence that the ubiquitin-proteasome system is involved in proopiomelanocortin/ACTH degradation in corticotropes. Indeed, proopiomelanocortin is a target of ubiquitylation and modulation of ubiquitin-proteasome system affects ACTH turnover. This study shows that regulation of ACTH proteolytic degradation may represent a means to control ACTH secretion.

Usefulness of desmopressin testing to predict relapse during long-term follow-up in patients in remission from Cushing's disease.

Recurrence of Cushing's disease after successful transsphenoidal surgery occurs in some 30% of the patients and the response to desmopressin shortly after surgery has been proposed as a marker for disease recurrence. The aim of the present study was to evaluate the response to desmopressin over time after surgery. We tested 56 patients with Cushing's disease in remission after transsphenoidal surgery with desmopressin for up to 20 years after surgery. The ACTH and cortisol response to desmopressin over time was evaluated in patients on long-term remission or undergoing relapse; an increase by at least 27 pg/mL in ACTH levels identified responders. The vast majority of patients who underwent successful adenomectomy failed to respond to desmopressin after surgery and this response pattern was maintained over time in patients on long-term remission. Conversely, a response to desmopressin reappeared in patients who subsequently developed a recurrence of Cushing's disease, even years prior to frank hypercortisolism. It appears therefore that a change in the response pattern to desmopressin proves predictive of recurrence of Cushing's disease and may indicate which patients require close monitoring.

Proopiomelanocortin, glucocorticoid, and CRH receptor expression in human ACTH-secreting pituitary adenomas.

ACTH-secreting pituitary tumors are by definition partially autonomous, i.e., secrete ACTH independent of physiological control. However, only few, small-sized studies on proopiomelanocortin (POMC) and its regulation by corticotropin-releasing hormone (CRH) or glucocorticoids are available. Objective of the present study was to report on constitutive and CRH- and dexamethasone-regulated POMC, CRH (CRH-R1), and glucocorticoid receptor (NR3C1) gene expression in a large series of human corticotrope adenomas. Fifty-three ACTH-secreting adenomas were incubated with 10 nM CRH or 10 nM dexamethasone for 24 h. POMC, CRH-R1, NR3C1, and its alpha and beta isoforms were quantified and medium ACTH measured. Constitutive POMC expression proved extremely variable, with macroadenomas exhibiting higher levels than microadenomas. POMC increased during CRH in most specimens; conversely, changes induced by dexamethasone were varied, ranging from decrease to paradoxical increase. No correlation between POMC and ACTH was detected in any experimental condition. CRH-R1 expression was not linked to the response to CRH while NR3C1 was expressed at greater levels in specimens who failed to inhibit during dexamethasone; glucocorticoid receptor α was the more abundant isoform and subject to down-regulation by dexamethasone. Our results demonstrate a considerable variability in POMC expression among tumors and no correlation between POMC and ACTH, suggesting that POMC peptide processing/transport plays a major role in modulating ACTH secretion. Further, CRH-R1 and NR3C1 expression were not linked to the expected ligand-induced outcome, indicating that receptor signaling rather than abundance determines corticotrope responses. Our findings pave the way to new avenues of research into Cushing's disease pathophysiology.

Effect of retinoic acid on human adrenal corticosteroid synthesis.

AIMS: Retinoic acid has recently yielded promising results in the treatment of Cushing's disease, i.e., excess cortisol secretion due to a pituitary corticotropin (ACTH)-secreting adenoma. In addition to its effect on the tumoral corticotrope cell, clinical results suggest an additional adrenal site of action. Aim of this study was to evaluate whether retinoic acid modulates cortisol synthesis and secretion by human adrenals in vitro. MAIN METHODS: Primary cultures from 10 human adrenals specimens were incubated with 10nM, 100nM and 1µM retinoic acid with and without 10nM ACTH for 24h. Cortisol levels were measured by radioimmunoassay and CYP11A1, STAR and MC2R gene expression analyzed by real-time PCR. KEY FINDINGS: Retinoic acid increased cortisol secretion (149.5±33.01%, 151.3±49.45% and 129.3±8.32% control secretion for 10nM, 100nM and 1µM respectively, p<0.05) and potentiated STAR expression (1.51±0.22, 1.56±0.15 and 1.59±0.14 fold change over baseline, for 10nM, 100nM and 1µM respectively, p<0.05). Concurrently, retinoic acid markedly blunted constitutional and ACTH-induced MC2R expression (0.66±0.11, 0.62±0.08 and 0.53±0.07 fold change over baseline, for 10nM, 100nM and 1µM respectively, p<0.05; 0.71±0.10, 0.51±0.07 and 0.51±0.08 fold change over ACTH alone, for 10nM, 100nM and 1µM respectively, p<0.05). No effect on CYP11A1 was observed. SIGNIFICANCE: Retinoic acid stimulates cortisol synthesis and secretion in human adrenals and at the same time markedly blunts ACTH receptor transcription. These results reveal a novel, adrenal effect of retinoic acid which may contribute to its efficacy in patients with Cushing's disease.

Bone turnover and mineral density in adult thalassemic patients: relationships with growth hormone secretory status and circulating somatomedins.

Previous evidence supports a role for growth hormone (GH)-insulin-like growth factor (IGF)-I deficiency in the pathophysiology of osteopenia/osteoporosis in adult thalassemia. Moreover, serum IGF-II has never been studied in this clinical condition. Thus, we elected to study the GH secretory status and the levels of circulating somatomedins, correlating these parameters with bone mineral density (BMD) and biochemical markers of bone turnover. A hundred and thirty-nine normal weight adult thalassemic patients (72 men and 67 women) were studied. Lumbar and femoral neck BMD were measured in 106/139 patients. Sixty-eight patients underwent growth hormone releasing hormone plus arginine testing. Measurement of baseline IGF-I and IGF-II was performed in all patients, while osteocalcin, C-terminal telopeptide of type I collagen (CTx), and urinary cross-linked N-telopeptides of type I collagen (NTx) were assayed in 95 of them. Femoral and lumbar osteoporosis/Z score below the expected range for age were documented in 61.3 and in 56.6 % of patients, respectively. Severe GH deficiency (GHD) was demonstrated in 27.9 % of cases, whereas IGF-I SDS was low in 86.3 %. No thalassemic patients displayed circulating levels of IGF-II below the reference range. GH peaks were positively correlated with femoral, but not lumbar, Z score. No correlations were found between GH peaks and osteocalcin, CTx and NTx. GH peaks were positively correlated with IGF-I values, which in their turn displayed a positive correlation with osteocalcin, CTx, and NTx. No correlations emerged between IGF-I values and either femoral or lumbar Z scores. No correlations were found between IGF-II and any of the following parameters: GH peaks, osteocalcin, CTx, NTx, femoral Z score, and lumbar Z score. Our study, besides providing for the first time evidence of a normal IGF-II production in thalassemia, contributes to a better understanding of the involvement of the somatotropin-somatomedin axis in the pathophysiology of bone demineralization in this disease. In particular, the contribution of GHD to femoral osteoporosis appears to be likely mediated by locally produced rather than circulating IGF-I.

No Untoward Effect of Long-Term Ketoconazole Administration on Electrocardiographic QT Interval in Patients with Cushing's Disease.

Ketoconazole is listed among drugs that prolong QT interval and may increase the risk of torsade de pointes, a severe ventricular arrhythmia. This compound has recently been approved for treatment of Cushing's syndrome, a severe endocrine disorder. These patients harbour several risk factors for prolonged QT interval, for example hypokalaemia and left ventricular hypertrophy, but no study has evaluated whether administration of ketoconazole affects their QT interval. The aim of this study was to assess the QT interval in patients with Cushing's disease during long-term administration of ketoconazole. Electrocardiograms from 15 patients with Cushing's disease (12 women, 3 men, age: 37.8 ± 2.66 years) on ketoconazole treatment (100 mg-800 mg qd) for 1 month to 12 years were reviewed retrospectively. QT interval was measured and corrected for heart rate (QTc). Measurements before and during ketoconazole treatment were compared and any abnormal QTc value recorded. Concurrent medical therapies were also documented. On average, QTc was superimposable before and during ketoconazole treatment (393.2 ± 7.17 versus 403.3 ± 6.05 msec. in women; 424.3 ± 23.54 versus 398.0 ± 14.93 msec. in men, N.S.). QTc normalized on ketoconazole in one man with prolonged QTc prior to treatment; no abnormal QTc was observed in any other patient during the entire observation period, even during concurrent treatment with other QT-prolonging drugs. In conclusion, long-term ketoconazole administration does not appear to be associated with significant prolongation of QT interval in patients with Cushing's disease. ECG monitoring can follow recommendations drawn for other low-risk QT-prolonging drugs with attention to specific risk factors, for example hypokalaemia and drug interactions.

AZA-deoxycytidine stimulates proopiomelanocortin gene expression and ACTH secretion in human pituitary ACTH-secreting tumors.

PURPOSE: It is well known that methylation plays an important role in regulating tissue expression of proopiomelanocortin (POMC) and recent studies have shown that demethylation can occur also in vitro in neuroendocrine tumors. Aim of the present study was to evaluate whether inhibition of methylation modulates POMC expression and ACTH secretion by human corticotrope tumors. METHODS: Twenty two ACTH-secreting pituitary tumors were incubated with 5-AZA-2'-deoxycytidine (AZA), an inhibitor of DNA-methyltransferases, with or without 10 nM corticotropin-releasing hormone (CRH). Both dose response (100 nM-10 µM AZA) and time course (4-96 h) experiments were carried out for measurement of ACTH secretion and POMC gene expression. RESULTS: Incubation with AZA increased constitutive POMC expression and ACTH secretion by human corticotrope adenomas. The effect appeared most notable at 24 and 48 h with 1 µM AZA. Incubation with AZA did not exert an additional stimulatory effect on CRH-stimulated POMC and ACTH. CONCLUSIONS: The present study shows that AZA increases POMC gene expression and ACTH secretion in human pituitary ACTH-secreting tumors. This can be taken to indicate that mechanisms set into motion by AZA play a role in the regulation of ACTH secretion/POMC expression in tumoral corticotropes and paves the way to further studies in Cushing's disease.

Gender-dependent changes in haematological parameters in patients with Cushing's disease before and after remission.

OBJECTIVE: Glucocorticoids stimulate several steps in red blood cell (RBC) development; however, little is known on changes in erythroid parameters in patients with Cushing's disease. The aim of this study was to assess both RBC and white blood cell (WBC) parameters in a large cohort of patients with Cushing's disease and report on alterations in the active phase and after surgical remission. DESIGN AND METHODS: A total of 80 patients with Cushing's disease (63 women and 17 men) were studied before and for up to 254 months' follow-up (mean follow-up 65.8 ± 6.71 months) after pituitary/adrenal surgery. Details of blood counts were reviewed and compared with data obtained from a database of healthy subjects. RESULTS: The RBC counts and haemoglobin levels were low in men with active Cushing's disease (over 80% of values in the lowest quartile) and four patients were overtly anaemic, whereas erythrocyte counts and haemoglobin levels were evenly distributed across the normal range in women with active Cushing's disease. Low erythroid parameters were linked to hypogonadism in men with Cushing's disease. Recovery in erythroid parameters occurred slowly after remission of hypercortisolism in men, in parallel with improvements in testosterone levels. Over 50% of patients with active disease presented increased WBC counts, irrespective of gender, and prompt normalisation within 1 month after surgery. CONCLUSIONS: Male patients with Cushing's disease present reduced RBC counts and haemoglobin levels, associated with low testosterone concentrations, which resolve over time after remission of hypercortisolism. Anaemia should therefore be regarded as another unfavourable feature in men with Cushing's disease.

Differential patterns of regional neuroadrenergic cardiovascular drive in acromegalic disease.

It has been shown that acromegaly is characterized by an autonomic imbalance and by marked sympathoinhibition. However, there is no information available as to whether adrenergic inhibition is confined to selected vascular districts or, rather, is generalized. We examined 17 newly diagnosed active acromegalic patients without hyperprolactinaemia, pituitary hormone deficiencies, obstructive sleep apnoea and cardiac hypertrophy and 14 healthy subjects matched for age, sex and body mass index. For each subject, we collected information regarding anthropometric parameters and echocardiography, and collected plasma samples to investigate anterior pituitary function, glucose and lipid metabolism and plasma leptin levels. Beat-to-beat mean arterial pressure, heart rate and efferent post-ganglionic muscle and skin sympathetic nerve traffic (MSNA and SSNA, respectively; determined by microneurography) were measured. Both MSNA and SSNA were recorded in a randomized sequence over two 30 min periods. Measurements also included evaluation of SSNA responses to emotional stimulus. In addition to significant reductions in plasma leptin levels, acromegalic patients had markedly decreased MSNA compared with the healthy controls. There were no significant differences in SSNA between the two groups, either under basal conditions or in responses to arousal stimuli. There was a significant and direct correlation between MSNA and plasma leptin levels, but not between plasma leptin and SSNA. These data provide the first evidence that the sympathetic inhibition characterizing the early phase of acromegaly is not generalized to the entire cardiovascular system.

Role of epigenetics in human aging and longevity: genome-wide DNA methylation profile in centenarians and centenarians' offspring.

The role of epigenetics in the modulation of longevity has not been studied in humans. To this aim, (1) we evaluated the DNA methylation from peripheral leukocytes of 21 female centenarians, their 21 female offspring, 21 offspring of both non-long-lived parents, and 21 young women through ELISA assay, pyrosequencing analysis of Alu sequences, and quantification of methylation in CpG repeats outside CpG islands; (2) we compared the DNA methylation profiles of these populations through Infinium array for genome-wide CpG methylation analysis. We observed an age-related decrease in global DNA methylation and a delay of this process in centenarians' offspring. Interestingly, literature data suggest a link between the loss of DNA methylation observed during aging and the development of age-associated diseases. Genome-wide methylation analysis evidenced DNA methylation profiles specific for aging and longevity: (1) aging-associated DNA hypermethylation occurs predominantly in genes involved in the development of anatomical structures, organs, and multicellular organisms and in the regulation of transcription; (2) genes involved in nucleotide biosynthesis, metabolism, and control of signal transmission are differently methylated between centenarians' offspring and offspring of both non-long-lived parents, hypothesizing a role for these genes in human longevity. Our results suggest that a better preservation of DNA methylation status, a slower cell growing/metabolism, and a better control in signal transmission through epigenetic mechanisms may be involved in the process of human longevity. These data fit well with the observations related to the beneficial effects of mild hypothyroidism and insulin-like growth factor I system impairment on the modulation of human lifespan.

Low circulating IGF-I bioactivity is associated with human longevity: findings in centenarians' offspring.

UNLABELLED: Centenarians' offspring represent a suitable model to study age-dependent variables (e.g. IGF-I) potentially involved in the modulation of the lifespan. The aim of the present study was to investigate the role of the IGF-I in human longevity. We evaluated circulating IGF-I bioactivity measured by an innovative IGF-I Kinase Receptor Activation (KIRA) Assay, total IGF-I, IGFBP-3, total IGF-II, insulin, glucose, HOMA2-B% and HOMA2-S% in 192 centenarians' offspring and 80 offspring-controls of which both parents died relatively young. Both groups were well-matched for age, gender and BMI with the centenarians' offspring. IGF-I bioactivity (p〈0.01), total IGF-I (p〈0.01) and the IGF-I/IGFBP-3 molar ratio (p〈0.001) were significantly lower in centenarians' offspring compared to offspring matched-controls. Serum insulin, glucose, HOMA2-B% and HOMA2-S% values were similar between both groups. In centenarians' offspring IGF-I bioactivity was inversely associated to insulin sensitivity. IN CONCLUSION: 1) centenarians' offspring had relatively lower circulating IGF-I bioactivity compared to offspring matched-controls; 2) IGF-I bioactivity in centenarians' offspring was inversely related to insulin sensitivity. These data support a role of the IGF-I/insulin system in the modulation of human aging process.

Potential role for retinoic acid in patients with Cushing's disease.

CONTEXT: Cushing's disease, i.e. cortisol excess due to an ACTH-secreting pituitary adenoma, is a rare disorder with considerable morbidity and mortality but no satisfactory medical treatment as yet. Experimental data have recently shown that retinoic acid restrains ACTH secretion by tumoral corticotropes. OBJECTIVE: Our objective was to evaluate the efficacy and safety profile of retinoic acid treatment in patients with Cushing's disease. DESIGN: This is a prospective, multicenter study. Seven patients with Cushing's disease (three men, four postmenopausal women) were started on 10 mg retinoic acid daily and dosage increased up to 80 mg daily for 6-12 months. ACTH, urinary free cortisol (UFC), and serum cortisol as well as clinical features of hypercortisolism and possible side effects of retinoic acid were evaluated at baseline, during retinoic acid administration, and after drug withdrawal. RESULTS: A marked decrease in UFC levels was observed in five patients; mean UFC levels on retinoic acid were 22-73% of baseline values and normalization in UFC was achieved in three patients. Plasma ACTH decreased in the first month of treatment and then returned to pretreatment levels in responsive patients whereas no clear-cut pattern could be detected for serum cortisol. Blood pressure, glycemia, and signs of hypercortisolism, e.g. body weight and facial plethora, were ameliorated to a variable extent on treatment. Patients reported only mild adverse effects, e.g. xerophthalmia and arthralgias. CONCLUSIONS: Long-term treatment with retinoic acid proved beneficial and well tolerated in five of seven patients with Cushing's disease. This represents a novel, promising approach to medical treatment in Cushing's disease.

Postprandial triglyceride profile after a standardized oral fat load is altered in growth hormone (GH)-deficient adult patients and is not improved after short-term GH replacement therapy.

OBJECTIVE: Adult growth hormone deficiency (GHD) has detrimental effects on metabolic profile, leading to an increased cardiovascular mortality and morbidity. Above all, disturbance in postprandial triglyceride metabolism is of major concern because of the crucial role of triglyceride-rich lipoproteins in atherogenesis. The majority of previous studies on GH replacement have shown favourable changes in the fasting lipid profile. Aim of this study is to investigate whether this beneficial effect is exerted also on postprandial triglyceride (TG) metabolism. PATIENTS AND METHODS: We challenged nine GHD patients with a standardized fat loading meal at baseline and after 6 months of GH replacement therapy. Nine healthy control subjects were similarly tested under baseline conditions. Blood samples were obtained before and up to 8 h after fat loading for serum lipid analysis. RESULTS: We found that GHD patients with fasting TG level in the normal range (1·29 ± 0·31 mm) had a delayed postprandial TG clearance compared to healthy controls (triglyceride level at 8 h, 3·82 ± 0·83 vs 1 ± 0·06 mm P < 0·01), and the postprandial hypertriglyceridaemia was not corrected by 6 months of GH therapy. CONCLUSIONS: This study has shown for the first time that GHD adult patients have a higher postprandial triglyceridaemia compared to healthy controls when challenged by a standardized fat load and that this atherogenic feature is not normalized by short-term GH treatment despite a decrease in visceral fat mass described during the replacement therapy.

The PPAR-γ agonist troglitazone antagonizes survival pathways induced by STAT-3 in recombinant interferon-ß treated pancreatic cancer cells.

We have previously shown that cancer cells can protect themselves from apoptosis induced by type I interferons (IFNs) through a ras→MAPK-mediated pathway. In addition, since IFN-mediated signalling components STATs are controlled by PPAR gamma we studied the pharmacological interaction between recombinant IFN-ß and the PPAR-γ agonist troglitazone (TGZ). This combination induced a synergistic effect on the growth inhibition of BxPC-3, a pancreatic cancer cell line, through the counteraction of the IFN-ß-induced activation of STAT-3, MAPK and AKT and the increase in the binding of both STAT-1 related complexes and PPAR-γ with specific DNA responsive elements. The synergism on cell growth inhibition correlated with a cell cycle arrest in G0/G1 phase, secondary to a long-lasting increase of both p21 and p27 expressions. Blockade of MAPK activation and the effect on p21 and p27 expressions, induced by IFN-ß and TGZ combination, were due to the decreased activation of STAT-3 secondary to TGZ. IFN-ß alone also increased p21 and p27 expression through STAT-1 phosphorylation and this effect was attenuated by the concomitant activation of IFNbeta-induced STAT-3-activation. The combination induced also an increase in autophagy and a decrease in anti-autophagic bcl-2/beclin-1 complex formation. This effect was mediated by the inactivation of the AKT→mTOR-dependent pathway. To the best of our knowledge this is the first evidence that PPAR-γ activation can counteract STAT-3-dependent escape pathways to IFN-ß-induced growth inhibition through cell cycle perturbation and increased autophagic death in pancreatic cancer cells.

Clinical relevance of cardiac structure and function abnormalities in patients with Cushing's syndrome before and after cure.

OBJECTIVES: Sustained hypercortisolism impacts cardiac function, and, indeed, cardiac disease is one of the major determinants of mortality in patients with Cushing's syndrome. The aim of this study was to assess the clinical relevance of cardiac structure and function alterations by echocardiography in patients with active Cushing's syndrome and after disease remission. STUDY DESIGN: Seventy-one patients (61 women, 10 men) with Cushing's syndrome and 70 age-, sex- and blood pressure-matched controls were enrolled. Echocardiography was performed in 49 patients with active disease and at several time points after remission in 44 patients (median follow-up 46.4 months), and prevalence of abnormal left ventricular mass measurements and systolic and diastolic functions indices was compared between patients with active disease, after remission and controls. Twenty-two patients were evaluated both before and after remission. RESULTS: Up to 70% of patients with active Cushing's syndrome presented abnormal left ventricular mass parameters; 42% presented concentric hypertrophy and 23% concentric remodelling. Major indices of systolic and diastolic functions, i.e. ejection fraction and E/A ratio, respectively, were normal. Upon remission of hypercortisolism, left ventricular mass parameters ameliorated considerably, although abnormal values were still more frequent than in controls. Both cortisol excess and hypertension contribute to cardiac mass alterations and increase the prevalence of target organ damage. CONCLUSIONS: Cushing's syndrome is associated with an increased risk for abnormalities of cardiac mass, which ameliorates, but does not fully disappear after remission. Systolic and diastolic functions are largely within the normal range in these patients.

High prevalence of prolonged QT interval in obese hypogonadal males.

Obese subjects show several electrocardiographic alterations, including prolonged QT interval, a marker for fatal cardiac arrhythmias. Prolonged QT interval has recently been linked to low testosterone levels, a frequent occurrence in male obese patients but no study has yet assessed whether hypoandrogenism contributes to QT interval prolongation in this population. Aim of this study was to evaluate whether prolonged QT interval is linked to hypogonadism in male obese subjects. QT interval corrected for heart rate (QTc) was measured from standard electrocardiogram recordings in 136 obese men (BMI 30 >kg/m(2), range 30.1-75.4 kg/m(2)). Obese men were classified as eugonadal or hypogonadal according to serum total testosterone levels (i.e., greater or less than 9.9 nmol/l). Our study showed that QTc measurements corrected by either Bazett (419 ± 3.2 vs. 408 ± 3.4 ms, P < 0.05), Fridericia (406.3 ± 3.39 vs. 396.4 ± 3.03 ms, P < 0.05) or Hodges (407.0 ± 3.12 vs. 397.3 ± 2.84 ms, P < 0.05) were longer in hypogonadal compared with eugonadal obese men; further, prolonged QTc interval (i.e., >440 ms) was more frequent among hypogonadal compared with eugonadal obese men (23% vs. 10%, P < 0.05). The degree of weight excess, diabetes, sleep apnoea and potassium levels were not associated with prolonged QTc. In conclusion, obese hypogonadal men show a greater prevalence of prolonged QT interval compared with their eugonadal counterparts. It appears therefore that low levels of testosterone in obese men may contribute to the arrhythmogenic profile of these patients, a heretofore unknown link which warrants further clinical attention.

Assessment of ACTH assay variability: a multicenter study.

OBJECTIVE: Measurement of plasma ACTH plays a pivotal role in the diagnosis and treatment of several endocrine disorders. Little is known, however, on the variability of ACTH assay results and its impact on clinical practice. The aim of the present study was to assess the performance of routine plasma ACTH measurements. DESIGN: Twenty-five fresh-frozen plasma samples collected from patients with either high, low, or normal ACTH concentrations were measured using seven different assays by 35 different laboratories. Assay precision, method agreement, and result classification were estimated. RESULTS: Inter- and intra-assay coefficient of variation varied considerably with some assays achieving <10%, others consistently achieving >20%. Overall method agreement was good (mean ratio versus target value 1.02) but subject to exceedingly large excursion (lower and upper limits of agreement at 0.13 and 1.91 respectively). Both differences between assays and between laboratories contributed to variability of method agreement. Assays correctly classified most patients with normal and high ACTH concentrations (90% (95% CI 82-97%) and 95% (95% CI 86-100%) respectively), whereas only 60% (95% CI 52-67%) of measurements from patients with low ACTH values were assigned correctly. CONCLUSIONS: Field ACTH assays have to be interpreted with caution as they are burdened by high variability and often fail to correctly identify patients with suppressed ACTH secretion. The endocrine community has to include ACTH assays among those requiring standardization.