Search

Several lumped element-based epsilon-negative (ENG), mu-negative (MNG), and double-negative (DNG) metamaterial designs have been developed for operation at 400 MHz in the UHF frequency band. The use of lumped elements enabled the creation of highly sub-wavelength unit cells whose overall size was λ0/d∼75 at 400 MHz. The measured negative index material (NIM) showed an effective real index of refraction nreal=-3.11 with a total loss that was less than 1 dB/cm. The NIM bandwidth was >10% in the neighborhood of 400 MHz. [ABSTRACT FROM AUTHOR]

Using numerical simulation techniques, the transmission and reflection coefficients, or S parameters, for left-handed metamaterials are calculated. Metamaterials consist of a lattice of conducting, nonmagnetic elements that can be described by an effective magnetic permeability μ[sub eff] and an effective electrical permittivity &Vegr;[sub eff], both of which can exhibit values not found in naturally occurring materials. Because the electromagnetic fields in conducting metamaterials can be localized to regions much smaller than the incident wavelength, it can be difficult to perform accurate numerical simulations. The metamaterials simulated here, for example, are based on arrays of split ring resonators (SRRs), which produce enhanced and highly localized electric fields within the gaps of the elements in response to applied time dependent fields. To obtain greater numerical accuracy we utilize the newly developed commercially available code MICROWAVE STUDIO, which is based on the finite integration technique with the perfect boundary approximation. The simulation results are in agreement with published experimental results for the frequencies and bandwidths of the propagation and stop bands associated with the various structures. We further analyze the properties of an individual SRR, and find the dependence of the resonant frequency on the SRR radius, ring thickness, inner/outer radial gap, azimuthal gap, electrical permittivity, and magnetic permeability of the components’ materials. Comparison with previously published analytical estimates shows only approximate agreement with the simulation results. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Objective: Recent studies investigated the prevalence of arterial hypertension (AH), diabetes mellitus (DM) and/or prediabetes, dyslipidemia (DL), metabolic syndrome (MS) and cardiovascular events (CVE) in patients with non-functioning adrenal incidentalomas (NFAI). We aimed to investigate the available literature to determine the prevalence of AH, DM, DM and/or prediabetes (Composite DM, C-DM), DL, MS and CVE in patients with NFAI as compared to patients without adrenal incidentalomas (AI)., Design: Systematic review and meta-analysis., Methods: A meta-analysis was performed using studies that evaluated the prevalence of AH, DM, C-DM, DL, MS and CVE in patients with NFAI versus matched subjects without AI. A random-effects model (DerSimonian and Laird) was used to calculate the pooled odds ratio (OR) and 95% Confidence Interval (95%CI) for each outcome., Results: Among the 36 available studies, 19 studies provided the necessary data (4716 subjects, mean age 57.6 ± 4.6). The association between AH, DM, C-DM, DL, MS and CVE was reported in 18 (4546 subjects), 7 (1743 subjects), 5 (4315 subjects), 11 (3820 subjects), 8 (1170 subjects) and 5 (2972 subjects), respectively. The presence of NFAI was associated with AH (OR 1.87, 95%CI 1.39-2.51), C-DM (OR 2.04, 95%CI 1.70-2.45) and MS (OR 2.89, 95%CI 1.93-4.32), but not with DM, DL and CVE., Conclusions: Patients with NFAI have higher prevalence of AH, C-DM and MS than control subjects without NFAI., (© 2024. The Author(s).)

Background: Pheochromocytoma is associated with systemic inflammation, but the underlying mechanisms are unclear. Therefore, we investigated the relationship between plasma metanephrine levels and haematological parameters - as a surrogate of inflammation - in patients with pheochromocytoma and the influence of preoperative α-blockade treatment., Design and Methods: We retrospectively studied 68 patients with pheochromocytoma who underwent adrenalectomy (median age 53 years, 64.7% females) and two control groups matched for age, sex, and body mass index (BMI): 68 patients with non-functioning adrenocortical tumors (NFAT) and 53 with essential hypertension (EAH). The complete blood count (CBC) and several inflammation-based scores [Neutrophil-to-Lymphocyte Ratio (NLR), Platelet-to-Lymphocyte Ratio (PLR), Lymphocyte-to-Monocyte Ratio (LMR), Systemic-Immune-Inflammation Index (SII), Prognostic-Nutrition Index (PNI)] were assessed in all patients and, in a subset of pheochromocytomas, after adrenalectomy (n=26) and before and after preoperative α-blockade treatment (n=29)., Results: A higher inflammatory state, as indicated by both CBC and inflammation-based scores, was observed in patients with pheochromocytoma compared to NFAT and EAH. Plasma metanephrine levels showed a positive correlation with NLR (r=0.4631), PLR (r=0.3174), SII (r=0.3709), and a negative correlation with LMR (r=0.4368) and PNI (r=0.3741), even after adjustment for age, sex, ethnicity, BMI and tumor size (except for PLR). After adrenalectomy, we observed a reduction in NLR (p=0.001), PLR (p=0.003), SII (p=0.004) and a concomitant increase in LMR (p=0.0002). Similarly, α-blockade treatment led to a reduction in NLR (p=0.007) and SII (p=0.03)., Conclusions: Inflammation-based scores in patients with pheochromocytoma showed pro-inflammatory changes that correlated with plasma metanephrine levels and are ameliorated by adrenalectomy and α-blockade., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Endocrine Society.)

The follow-up strategy for unresected non-functional adrenal tumors (NFAT) is a major controversial issue in endocrinological clinical practice, as the natural history of adrenal incidentalomas (AI) is partially unknown and a consensus on their adequate management is lacking. In a recent longitudinal study by Ceccato et al., a large cohort of patients with conservatively treated AI were evaluated for possible radiological variations over time and their relationship with autonomous cortisol secretion (ACS). Starting from this paper, we performed a literature review of available longitudinal studies focus on the same issue. Notwithstanding the high variability in the duration of follow-up and in the criteria used to define ACS in the included studies, our findings support the idea that there is a not negligible risk of morphological and functional changes, which may have metabolic implications, especially after 5-10 years of follow-up. Unfortunately, these variations seem to be scarcely predictable. Therefore, it may be risky to interrupt the follow-up in patients with NFAT, in particular in the presence of larger diameter of the adenoma and higher cortisol levels at diagnosis. These results should be considered in defining the optimal management of these patients., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Parazzoli, Favero, Aresta and Morelli.)

Background: Similarly to cortisol-secreting adrenal tumors, also non-functioning adrenal tumors (NFAT) may be associated with an increased cardiovascular risk. We assessed in NFAT patients: (i) the association between hypertension (HT), diabetes mellitus (DM), obesity (OB), dyslipidemia (DL) and cardiovascular events (CVE) and cortisol secretion; (ii) the cut-off of the cortisol secretion parameters for identifying NFAT patients with a worse cardiometabolic profile., Patients and Methods: In 615 NFAT patients (with cortisol levels after 1 mg overnight dexamethasone suppression test, F-1mgDST < 1.8 µg/dL [50 nmol/L]) F-1mgDST and adrenocorticotroph hormone (ACTH) levels and data on HT, DM, OB, DL and CVEs prevalence were retrospectively collected., Results: HT, DM and HT plus DM were associated with F-1mgDST levels (area under the ROC curve: 0.588 ± 0.023, 0.610 ± 0.028, 0.611 ± 0.033, respectively, p < 0.001 for all comparisons) but not with ACTH. The cut-off for identifying patients with either HT or DM or HT plus DM was set at ≥ 1.2 µg/dL (33 nmol/L). As compared with patients with F-1mgDST < 1.2 µg/dL (n = 289), patients with F-1mgDST 1.2-1.79 µg/dL (33-49.4 nmol/L) (n = 326) had lower ACTH levels (17.7 ± 11.9 vs 15.3 ± 10.1 pg/mL, respectively, p = 0.008), older age (57.5 ± 12.3 vs 62.5 ± 10.9 years, respectively, p < 0.001), and higher prevalence of HT (38.1% vs 52.5% respectively p < 0.001), DM (13.1% vs 23.3%, respectively, p = 0.001), HT plus DM (8.3% vs 16.9%, respectively, p < 0.002) and CVE (3.2% vs 7.3%, respectively, p = 0.028). F-1mgDST 1.2-1.79 µg/dL was associated with either HT (odd ratio, OR, 1.55, 95% confidence interval, 95% CI 1.08-2.23, p = 0.018) or DM (OR 1.60, 95% CI 1.01-2.57, p = 0.045) after adjusting for age, gender, OB, DL, and DM (for HT) or HT (for DM), and with the presence of HT plus DM (OR 1.96, 95% CI 1.12-3.41, p = 0.018) after adjusting for age, gender, OB and DL., Conclusions: In NFAT patients, F-1mgDST 1.2-1.79 µg/dL seems to be associated with a higher prevalence of HT and DM and a worse cardiometabolic profile, even if the poor accuracy of these associations suggests caution in interpreting these results., (© 2023. The Author(s).)

Mild hypercortisolism is defined as biochemical evidence of abnormal cortisol secretion without the classical detectable manifestations of overt Cushing's syndrome and, above all, lacking catabolic characteristics such as central muscle weakness, adipose tissue redistribution, skin fragility and unusual infections. Mild hypercortisolism is frequently discovered in patients with adrenal incidentalomas, with a prevalence ranging between 5 and 50%. This high variability is mainly due to the different criteria used for defining this condition. This subtle cortisol excess has also been described in patients with incidentally discovered pituitary tumors with an estimated prevalence of 5%. To date, the mechanisms responsible for the pathogenesis of mild hypercortisolism of pituitary origin are still not well clarified. At variance, recent advances have been made in understanding the genetic background of bilateral and unilateral adrenal adenomas causing mild hypercortisolism. Some recent data suggest that the clinical effects of glucocorticoid (GC) exposure on peripheral tissues are determined not only by the amount of the adrenal GC production but also by the peripheral GC metabolism and by the GC sensitivity. Indeed, in subjects with normal cortisol secretion, the combined estimate of cortisol secretion, cortisone-to-cortisol peripheral activation by the 11 beta-hydroxysteroid dehydrogenase enzyme and GC receptor sensitizing variants have been suggested to be associated with the presence of hypertension, diabetes and bone fragility, which are three well-known consequences of hypercortisolism. This review focuses on the pathophysiologic mechanism underlying both the different sources of mild hypercortisolism and their clinical consequences (bone fragility, arterial hypertension, subclinical atherosclerosis, cardiovascular remodeling, dyslipidemia, glucose metabolism impairment, visceral adiposity, infections, muscle damage, mood disorders and coagulation).

Adrenal incidentalomas (AI) may be associated with a mild autonomous cortisol secretion (MACS) in up to one third of cases. There is growing evidence that MACS patients actually present increased risk of cardiovascular disease and higher mortality rate, driven by increased prevalence of known cardiovascular risk factors, as well as accelerated cardiovascular remodelling. Adrenalectomy seems to have cardiometabolic beneficial effects in MACS patients but their management is still a debated topic due to the lack of high-quality studies. Several studies suggested that so called "non-functioning" AI may be actually "functioning" with an associated increased cardiovascular risk. Although the individual cortisol sensitivity and peripheral activation have been recently suggested to play a role in influencing the cardiovascular risk even in apparently eucortisolemic patients, to date the degree of cortisol secretion, as mirrored by the cortisol levels after dexamethasone suppression test remains the best predictor of an increased cardiovascular risk in AI patients. However, whether or not the currently used cut-off set at 50 nmol/L for cortisol levels after dexamethasone suppression could be considered completely reliable in ruling out hypercortisolism remains unclear., Competing Interests: Declaration of competing interest Iacopo Chiodini has received speaker and consultancy fees from HRA pharma and Corcept. The other authors have no conflict of interest concerning this review article., (Copyright © 2021 Elsevier Ltd. All rights reserved.)