86,823 research outputs found
Corticotropin-releasing hormone is produced by rat corticotropes and modulates ACTH secretion in a paracrine/autocrine fashion
No full textAnterior pituitary hormone secretion is mainly regulated by hypothalamic releasing factors, which reach the pituitary via portal vessels. It has been demonstrated recently that these peptides can also be produced by the pituitary itself, thus possibly modulating hormone secretion in a paracrine/autocrine fashion. The object of this study was to seek evidence for the synthesis and secretion of corticotropin-releasing hormone (CRH) within the anterior pituitary and to ascertain its biological relevance. Messenger RNA from adult rat anterior pituitary fragments and cell cultures was reverse transcribed and subjected to PCR amplification using primers specific to the rat CRH gene. As in the hypothalamus, a single 232-bp band was obtained. The correspondence of the amplified fragment to the sequence of the CRH gene was confirmed by Southern blotting and restriction enzyme digestion. Combined in situ reverse transcription-PCR amplification/immunocytochemistry demonstrated the presence of CRH mRNA in corticotropes. Medium from anterior pituitary primary cultures contained approximately 7 pg/microg protein of CRH immunoreactivity which presented the same chromatographic profile on HPLC as the mature CRH peptide. Incubation of anterior pituitary cells with an antibody directed against CRH markedly reduced basal ACTH secretion compared with serum-treated control wells (0.89+/-0.11 vs. 1.74+/-0.14 ng/200,000 cells in control wells after 1 h, P < 0.05; 1.17+/-0.10 vs. 2.16+/-0. 39 ng/200,000 cells after 2 h, P < 0.05; 1.45+/-0.12 vs. 3.12+/-0.61 ng/200,000 cells after 3 h, P < 0.05). Further, the ACTH response to potassium and to forskolin was markedly blunted by the CRH antiserum as well as by the CRH antagonist, alpha-helical CRH(9-41). In conclusion, this study demonstrates the presence of CRH mRNA in normal rat corticotropes and the secretion of the mature peptide by the anterior pituitary, pointing to the production of CRH at the site of its target cells. In addition, intrapituitary CRH contributes in a paracrine/autocrine fashion to ACTH secretion
Epidemiology and follow-up of Cushing's disease
No full textLittle is known on the epidemiology of Cushing's disease (CD) as relevant data on such a rare disease can only be obtained from large-scale studies. We addressed this topic analyzing the data obtained in the Italian multicenter study which comprised nearly 300 patients with CD. The number of newly diagnosed patients with CD increased markedly in the second decade of the study (from 7.4 +/- 0.71 pts/year prior to 1987 to 26.4 +/- 4.12 after 1987) probably reflecting the heightened awareness of the disease and the increased availability of diagnostic tools. Urinary free cortisol (UFC) levels were significantly higher in men than in women and were inversely correlated with the time interval between appearance of symptoms and diagnosis. Recognition of CD among patients presenting with common diseases such as obesity, diabetes and hypertension requires highly sensitive screening tests (e.g. UFC, midnight cortisol in saliva, overnight dexamethasone suppression test) which however may yield false positive results. In doubt, second line testing using dex-CRH or desmopressin may distinguish between CD and pseudo Cushing. The different prevalence of CD and ectopic ACTH secretion (ES) undermines the diagnostic accuracy of tests used for the differential diagnosis of ACTH-dependent Cushing's syndrome (i.e. CRH, high dose dexamethasone, IPSS). Tests aimed at identifying ES rather than CD are needed to overcome this bias. Transsphenoidal surgery was the preferred choice of treatment for patients with CD, resulting in remission in 70% operated patients with a 15% relapse rate over 10 years follow-up. Definition of remission after surgery and parametres predictive of relapse, however, vary according to studies and long-term follow-up is required to establish their validity. Most clinical manifestations of hypercortisolism disappeared after remission although some long-lasting effects on the cardiovascular system had been observed. Finally, according to recent reports, mortality rates for patients cured of CD appear comparable to those of the general population
Transsphenoidal surgery for Cushing's disease : importance of histopathology for prediction of outcome
No full textAcromegaly
No full textAcromegaly is a slowly progressive disease characterized by 30% increase of mortality rate for cardiovascular disease, respiratory complications and malignancies. The estimated prevalence of the disease is 40 cases/ 1000000 population with 3-4 new cases/1000000 population per year. The biochemical diagnosis is based upon the demonstration of high circulating levels of GH and IGF-I. A random GH level lower than 0.4 (mu)g/l and an IGF-I value in the age- and sex-matched normal range makes the diagnosis of acromegaly unlikely. In doubtful cases, the lack of GH suppressibility below 1 (mu)g/l (0.3 (mu)g/l according to recent reports) after an oral glucose load will confirm the diagnosis. A pituitary adenoma is demonstrated in most cases by CT scan or MRI. A negative X-ray finding or the presence of empty sella do not exclude the diagnosis. Cardiovascular complications (acromegalic cardiomyopathy and arterial hypertension) should be looked for and, if present, followed-up by echocardiography and 24 h-electrocardiogram. Sleep apnoea, when clinically suspicious, should be confirmed by polisomnography. At the moment of diagnosis all patients should undergo colonscopy. Lipid profile should be obtained and glucose tolerance evaluated. Surgery, radiotherapy and medical treatment represent the therapeutic options for acromegaly. The outcome of transsphenoidal surgery is far better for microadenomas (80-90%) than for macroadenomas (less than 50%), which unluckily represent more than 70% of all GH-secreting pituitary tumours. Therefore, pituitary surgery is the first line treatment for microadenomas. Medical therapy is based on GH-lowering drugs (somatostatin receptor agonists and, in some cases, dopaminergic agents) and GH receptor antagonists (pegvisomant). The former are traditionally indicated after unsuccessful surgery and while awaiting the effectiveness of radiation therapy. However, GH-lowering drugs are also used as primary therapy when surgery is contraindicated or in the case of large GH-secreting macroadenomas which are not likely to be completely removed by surgery. These compounds may also be indicated in the preoperative management of some acromegalic patients in order to lower the risk of surgical and anaesthetic complications. For the moment pegvisomant is indicated for patients resistant to the GH-lowering drugs and there is no evidence for drug-induced enlargement of the pituitary tumour. In order to avoid this possibility, however, a combination of pegvisomant and GH-lowering compound can also be conceived. With pegvisomant, IGF-I plasma levels are the marker of therapeutic efficacy and normalize in 97% of patients. Radiotherapy is employed sparingly due to the number of side effects (80% of hypopituitarism). It is indicated after unsuccessful surgical and/or medical treatment and allows the control of hormonal secretion and tumour growth in approx. 40% and 100% of cases, respectively. Acromegaly is defined as controlled when, in the absence of clinical activity, IGF-I levels are in the age- and sex-matched normal range and GH is normally suppressible by the oral glucose load
Advances in the medical management of Cushing's syndrome
No full textBackground: Management of Cushing's syndrome, that is, excess cortisol secretion, has undergone considerable advances since the pioneering studies by Harvey Cushing. Surgery is clearly first choice for all etiologies of Cushing's syndrome, and medical therapy is largely administered in the interim between other therapeutic options. The limited use of medical therapy is a consequence of the lack of a truly efficacious compound to restrain adrenocorticotrophic hormone or cortisol secretion, but this will hopefully change in the near future as molecules developed over the past few years are tested. Conclusion: This paper illustrates present and perspective medical treatments for Cushing's syndrome
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