Andreea Picu

Effect of protracted treatment with rosiglitazone, a PPARgamma agonist, in patients with Cushing's disease.

Objective  Cushings disease, hypercortisolism due to a pituitary ACTH‐secreting tumour, is a highly morbid illness as yet without effective medical therapy. Recent studies have demonstrated that peroxisome proliferator‐activated receptor gamma (PPARγ) agonists effectively suppress ACTH secretion in a murine tumoral corticotroph cell line, but the few studies conducted so far in patients with ACTH‐secreting pituitary adenomas have yielded variable results.

Neuroregulation of the Hypothalamus-Pituitary-Adrenal (HPA) Axis in Humans: Effects of GABA-, Mineralocorticoid-, and GH-Secretagogue-Receptor Modulation

The hypothalamus-pituitary-adrenal (HPA) axis exerts a variety of effects at both the central and peripheral level. Its activity is mainly regulated by CRH, AVP, and the glucocorticoid-mediated feedback action. Moreover, many neurotransmitters and neuropeptides influence HPA axis activity by acting at the hypothalamic and/or suprahypothalamic level. Among them, GABA and Growth Hormone Secretagogues (GHS)/GHS-receptor systems have been shown to exert a clear inhibitory and stimulatory effect, respectively, on corticotroph secretion. Alprazolam (ALP), a GABA-A receptor agonist, shows the most marked inhibitory effect on both spontaneous and stimulated HPA axis activity, in agreement with its peculiar efficacy in panic disorders and depression where an HPA axis hyperactivation is generally present. Ghrelin and synthetic GHS possess a marked ACTH/cortisol-releasing effect in humans and the ghrelin/GHS-R system is probably involved in the modulation of the HPA response to stress and nutritional/metabolic variations. The glucocorticoid-mediated negative feedback action is mediated by both glucocorticoid (GR) and mineralocorticoid (MR) receptors activation at the central level, mainly in the hippocampus. In agreement with animal studies, MRs seem to play a crucial role in the maintenance of the circadian ACTH and cortisol rhythm, through the modulation of CRH and AVP release. GABA agonists (mainly ALP), ghrelin, as well as MR agonists/antagonists, may represent good tools to explore the activity of the HPA axis in both physiological conditions and pathological states characterized by an impaired control of the corticotroph function.

Long-term morphological, hormonal, and clinical follow-up in a single unit on 118 patients with adrenal incidentalomas.

OBJECTIVE To evaluate long-term morphological, functional, and clinical outcome in adrenal incidentalomas. DESIGN AND METHODS A total of 118 patients (77 F and 47 M; age 62.3+/-1.0 years) with adrenal incidentalomas were evaluated at baseline and followed-up for median 3 years (range 1-10 years) by clinical, biochemical, hormonal, and morphological evaluation. Among them, six patients with diagnosis of subclinical Cushings syndrome (SCS) underwent surgery. RESULTS At entry, 86% (n=102) of tumors were nonfunctioning (NF) and 14% (n=16) showed SCS. Comparing NF with SCS patients, a significantly higher percentage of dyslipidemia was found in the group of SCS patients (50 vs 23%, P=0.033). During follow-up, adrenal function remained normal in all NF patients, none of them developed subclinical or overt endocrine disease. The cumulative risk of mass enlargement was globally low (25%), but progressive up to 8 years. SCS was confirmed in all patients, and none of them shifted to overt Cushings syndrome. The cumulative risk of developing metabolic-cardiovascular abnormalities was globally low (22%), but progressive up to 8 years and new diseases were recorded in the group of NF patients only (three patients with dyslipidemia, four with impaired fasting glucose/impaired glucose tolerance, and three with diabetes mellitus). SCS patients who underwent surgery did not show any significant clinical improvement. CONCLUSIONS The risk of mass enlargement, hormonal, and metabolic impairment over time is globally low. Conservative management seems to be appropriate, but further prospective studies are needed to establish the long-term outcome of such patients, especially for metabolic status, cardiovascular risk profile and their relationship with endocrine function.

Hypothalamus–pituitary–adrenal axis evaluation in patients with hypothalamo–pituitary disorders: comparison of different provocative tests

Background  The insulin tolerance test (ITT) is the gold standard test to evaluate hypothalamic–pituitary–adrenal (HPA) axis in suspected ACTH insufficiency. When contraindicated, alternative tests have been proposed such as metyrapone and ACTH stimulation test. 250 µg ACTH is a supramaximal dose and unreliable in this setting. The diagnostic reliability of 1·0 µg ACTH test is controversial and very low doses have been proposed.

Metabolic and cardiovascular outcomes in patients with Cushing’s syndrome of different aetiologies during active disease and 1 year after remission

Objective  Cushing’s syndrome is associated with several comorbidities responsible for the increased cardiovascular risk, not only during the active phase but also after disease remission.

Ghrelin, Hypothalamus-Pituitary-Adrenal (HPA) Axis and Cushing's Syndrome

Ghrelin, a peptide predominantly produced by the stomach, has been discovered as a natural ligand of the GH Secretagogue receptor type 1a (GHS-R1a), known as specific for synthetic GHS. Ghrelin has recently attracted considerable interest as a new orexigenic factor. However, ghrelin exerts pleiotropic actions that are explained by the widespread distribution of ghrelin and GHS-R expression. Besides strong stimulation of GH secretion, the neuroendocrine ghrelin actions also include significant stimulation of both lactotroph and corticotroph secretion; all these actions depend on acylation of ghrelin in serine-3 that allows binding and activation of the GHS-R1a. However, GHS-R subtypes are likely to exist; they also bind unacylated ghrelin that is, in fact, the most abundant circulating form and exerts some biological actions. Ghrelin secretion is mainly regulated by metabolic signals, namely inhibited by feeding, glucose and insulin while stimulated by energy restriction. The role of glucocorticoids on ghrelin synthesis and secretion is still unclear although morning ghrelin levels have been found reduced in some patients with Cushings syndrome; this, however, would simply reflect its negative association to body mass. Ghrelin, like synthetic GHS, stimulates ACTH and cortisol secretion in normal subjects and this effect is generally sensitive to the negative glucocorticoid feedback. It is remarkable that, despite hypercortisolism, ghrelin as well as synthetic GHS display marked increase in their stimulatory effect on ACTH and cortisol secretion in patients with Cushings disease. This is even more intriguing considering that the GH response to ghrelin and GHS is markedly reduced by glucocorticoid excess. It has been demonstrated that the ACTH-releasing effect of ghrelin and GHS is purely mediated at the central level in physiological conditions; its enhancement in the presence of ACTH-secreting tumours is, instead, likely to reflect direct action on GHS receptors present on the neoplastic tissues. In fact, peculiar ACTH hyperresponsiveness to ghrelin and GHS has been observed also in ectopic ACTH-secreting tumours.

Glucose metabolism in patients with subclinical Cushing’s syndrome

This clinical review will summarize the available data regarding the effect of either physiological or increased glucocorticoid concentrations on glucose metabolism and insulin-sensitivity, in order to clarify the role, if any, of subclinical Cushing’s syndrome (SCS), a status of altered hypothalamic–pituitary–adrenal axis secretion in the absence of the classical signs or symptoms of overt cortisol excess, in patients with adrenal incidentalomas (AI) and diabetes mellitus type 2. Focusing on patients with SCS associated to AI, while there is convincing evidence in the literature that even a mild hyper cortisolemia is associated with alterations of glucose metabolism, evidence is insufficient to conclude that the simple correction of chronic, even mild, hypercortisolism can completely revert metabolic, mainly glycemic alterations. At the same time, considering the variability of the prevalence of Cushing’s syndrome in patients with diabetes mellitus type 2 reported in the literature, no agreement does exist whether screening for CS can be useful and recommended in those patients.

Effect of acute and prolonged mineralocorticoid receptor blockade on spontaneous and stimulated hypothalamic–pituitary–adrenal axis in humans

CONTEXT Mineralocorticoid receptors (MRs) in the hippocampus display an important role in the control of the hypothalamic-pituitary-adrenal (HPA) axis, mediating the proactive feedback of glucocorticoids, which maintains the basal HPA activity. The systemic administration of MR antagonists enhances spontaneous and CRH-stimulated ACTH, cortisol, and DHEA secretion, while the effects of chronic treatment with MR antagonists are scanty. Our study was performed in order to clarify this point. DESIGN ACTH, cortisol, and DHEA levels were studied during the infusion of placebo, canrenoate, a MR antagonist (CAN, 200 mg i.v. bolus at 1600 h followed by 200 mg infused over 4 h), and human CRH (hCRH; 2.0 microg/kg i.v. bolus at 1800 h) before and during the last week of 28-day treatment with CAN (200 mg/day p.o.) in eight young women. RESULTS Pre-treatment sessions: CAN and hCRH administration increased ACTH, cortisol, and DHEA levels versus placebo (P<0.05). Post-treatment sessions: during placebo infusion, cortisol and DHEA were significantly amplified versus pre-treatment session (P<0.05), while ACTH levels were not modified; CAN infusion, differently from pre-treatment session, was not able to significantly increase ACTH, cortisol, and DHEA levels; ACTH, cortisol, and DHEA responses to hCRH were amplified with respect to pre-treatment session, although statistical significance was obtained for cortisol and DHEA only. CONCLUSIONS MR blockade by acute CAN administration significantly enhances the HPA activity in the afternoon, during the quiescent phase of the circadian rhythm. At the same period, prolonged treatment with CAN amplifies both spontaneous and CRH-stimulated activities of the HPA axis, while it blunts the HPA responsiveness to a further MR-mediated stimulation.

Ghrelin does not mediate the somatotroph and corticotroph responses to the stimulatory effect of glucagon or insulin-induced hypoglycaemia in humans

objective  Acylated ghrelin, a gastric peptide, possesses a potent GH‐ but also significant ACTH/cortisol‐releasing activity mediated by the activation of GH secretagogue receptors (GHS‐R) at the hypothalamus–pituitary level. The physiological role of ghrelin in the control of somatotroph and corticotroph function is, however, largely unclear. Glucagon is known to induce a clear increase of GH, ACTH and cortisol levels in humans, at least after intramuscular administration. In fact, glucagon is considered to be a classical alternative to insulin‐induced hypoglycaemia (ITT) for the combined evaluation of the function of GH and the hypothalamus–pituitary–adrenal (HPA) axis. We aimed to clarify whether ghrelin mediate the GH and corticotroph responses to intramuscular glucagon or ITT, which has recently been reported able to induce a surprising ghrelin decrease.

Do muscle fiber conduction slowing and decreased levels of circulating muscle proteins represent sensitive markers of steroid myopathy? A pilot study in Cushing's disease

OBJECTIVE Glucocorticoids are known to decrease protein synthesis and conduction velocity of muscle fibers. However, the degree of impairment of muscle protein synthesis and conduction slowing in patients with Cushings disease remains poorly characterized. Our objective was to investigate whether and to what extent chronic endogenous hypercortisolism could decrease the circulating levels of muscle proteins and modify myoelectric indexes of sarcolemmal excitability and fatigability. DESIGN A total of ten patients with Cushings disease and 30 healthy controls matched for age, sex, and body mass index were compared. METHODS Blood sampling and electrophysiological tests on vastus lateralis, vastus medialis, and tibialis anterior muscles were performed. RESULTS Serum creatine kinase (CK) and plasma myoglobin were significantly lower in patients with respect to controls (P<0.001 and P<0.05 respectively): the mean relative difference between patients and controls was 48.9% for CK and 21.4% for myoglobin. Muscle fiber conduction velocity (MFCV) and myoelectric manifestations of fatigue were significantly decreased in all muscles of the patients with respect to controls. The mean relative difference in MFCV between patients and controls was 26.0% for vastus lateralis, 22.9% for vastus medialis, and 11.6% for tibialis anterior. These differences contrasted with the paucity of signs suggestive of myopathy that were obtained by needle electromyography in the patients. CONCLUSIONS Slowing of muscle fiber conduction and decreased levels of circulating muscle proteins are sensitive markers of impaired muscle function, which are suitable for use in combination with clinical assessment and standard electrodiagnostic tests for accurate identification and follow-up of myopathic patients.