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Biomedical subjects

P Chanson

Publications and source records attributed to P Chanson.

At least 55 records · Page 3Linked to original sources
PubMed1998

Absence of activating mutations in the GnRH receptor gene in human pituitary gonadotroph adenomas.

The monoclonal origin of gonadotropin-secreting pituitary adenomas has been well demonstrated but only few molecular abnormalities have so far been recognized in these tumors. For many years, several authors have suggested a role for GnRH and/or GnRH receptors (GnRH-R) in the development of these pituitary adenomas. To test the hypothesis that mutant genes encoding a constitutively activated GnRH-R might be involved in the pathogenesis of these tumors, the sequence of the GnRH-R gene was analyzed in tumoral pituitary tissue obtained from ten patients (six female, four male). The pituitary gonadotropin-secreting adenoma was associated with in vivo hypersecretion of FSH, LH and/or free alpha-subunit (n = 7) or was clinically silent (normal plasma levels of gonadotropins or free alpha-subunit, n = 3). In all cases, immunocytochemical studies of the removed adenoma confirmed their gonadotroph nature by revealing positivity for FSH, LH and/or alpha-subunit. Genomic DNA was extracted from the pathological tissue obtained at neurosurgery. Eight sequencing primers were used to amplify the three exons of the GnRH-R gene from tumoral DNA. The entire coding sequence of the GnRH-R gene was sequenced in the ten adenomas. No mutation was found in any of the tumor specimens examined. In conclusion, mutations in the GnRH receptor coding sequence occur infrequently if at all in gonadotropin-secreting pituitary adenomas.

Adenoma↗
PubMed1997

Management of patients and subjects at risk for multiple endocrine neoplasia type 1: MEN 1. GENEM 1. Groupe d'Etude des Néoplasies Endocriniennes Multiples de type 1.

Multiple endocrine neoplasia type 1 (MEN 1) is characterized by the combined occurrence, to variable degree, of hyperparathyroidism (HPT) (85.7% of cases according to the French Registry of GENEM 1), tumors of the endocrine pancreas (49.6%), pituitary adenomas (38.4%) and, less frequently, adrenal tumors (9.6%) and neuroendocrine tumors (5.8%). Currently, diagnosis of MEN 1 is done in the fourth decade of life, but familial screening (using genetic tools whose diagnostic accuracy approaches 100%) has lowered the age of diagnosis. Screening for MEN 1 in a patient harboring an apparently sporadic tumor will depend on the endocrine gland involved. Extensive screening for MEN 1 in the presence of HPT will be conducted only when the familial history is suggestive, when parathyroid glands are hyperplastic or when multiple parathyroid adenomas have been found at surgery. All patients with an endocrine pancreas tumor need to be investigated for the presence of other endocrine lesions of MEN 1. Extensive screening for MEN 1 is only recommended when a patient with a pituitary tumor or an adrenal tumor has a familial history suggestive of MEN 1. Otherwise regular measurement of blood calcium and PTH levels seem sufficient. Extensive screening for endocrine lesions when MEN 1 is suspected involves hormone measurements and imaging procedures. For the diagnosis of HPT, calcemia and PTH 1-84 must be measured. In the absence of clinical symptoms, basal measurement of serum gastrin, glucose, insulin, glucagon, VIP, somatostatin and pancreatic polypeptide levels are combined with abdominal ultrasonography. When symptoms suggest the Zollinger-Ellison syndrome, the secretin stimulation test is recommended. The diagnosis of a pituitary tumor is made by pituitary imaging and selected hormone assays (mainly PRL). To detect an adrenal tumor, CT scan is recommended, combined with serum potassium, urinary free cortisol and androgen measurement. When the diagnosis of MEN 1 is made, clinical and hormonal follow-up (once a year) and imaging surveillance (every 3-5 years) may be sufficient to detect new other endocrinopathies (unless suggestive clinical symptoms arise). Surgical management of each endocrine lesion must be done by skilled surgeons according to therapeutic protocols which have been discussed in detail. Genetic screening is an integral part of familial screening which may be conducted in collateral and in the offspring of MEN 1 patients. Obviously ethical principles (informed consent, etc.) must be respected. As it is now possible to detect presymptomatic gene carriers with a high degree of accuracy, follow-up is needed to make appropriate management decisions. The marked anxiety provoked by screening in an overtly asymptomatic healthy subject must not be underestimated. Conversely, a negative genetic diagnosis helps to reassure the subject and avoid repetitive and costly follow-up.

France↗
PubMed1997

Free luteinizing-hormone beta-subunit in normal subjects and patients with pituitary adenomas.

Most clinically nonfunctioning pituitary adenomas (NFPA) are found to be gonadotropinomas when assessed by immunocytochemistry. However, they are rarely associated with increased basal plasma levels of FSH, LH and/or alpha-subunit. It has been claimed that the paradoxical free LHbeta response to TRH may be a useful clinical tool for determining the gonadotropic nature of NFPA. We used a very specific and sensitive immunoradiometric assay (IRMA) for free LHbeta measurement and another specific IRMA to check the absence of free CGbeta, to study normal subjects and 26 patients with NFPA. Basal plasma levels of LHbeta were undetectable in normal men and premenopausal women in the early follicular phase. In contrast, normal postmenopausal women had increased basal plasma LHbeta, parallel to dimeric LH and alpha-subunit levels. In healthy subjects, stimulation with GnRH elicited an increase in LHbeta while TRH was ineffective. In patients with NFPA, LHbeta hypersecretion was found basally and/or after stimulation with TRH in 3 of 16 men, 3 of 5 premenopausal women, and 1 of 5 postmenopausal women, i.e. 7 of 26 patients (26%). In 3 of these 7 cases, alpha-subunit and/or FSH levels were also increased. The LHbeta measurement was thus truly informative on the gonadotropic nature of NFPA in only 4 out of 26 cases (15%). In addition, increased LHbeta levels and/or a positive response of free LHbeta to TRH was observed in 3 patients with pure prolactinomas but in no patients with GH-secreting adenomas. Thus, using this very sensitive and specific IRMA, free LHbeta measurement is rarely helpful for determining the gonadotropic nature of NFPA.

Acromegaly↗
PubMed1997

Panhypopituitarism as a model to study the metabolism of dehydroepiandrosterone (DHEA) in humans.

The physiological importance and therapeutical interest of dehydroepiandrosterone (DHEA) and its sulfate ester (DHEAS) are still controversial. Panhypopituitarism is characterized by the absence of secretion of adrenal and gonadal steroids and thus the production of their metabolites. The conversion of DHEA given orally into delta 5 derivatives, androgens, androgen metabolites, and estrogens was studied in ten patients with complete panhypopituitarism. Sex steroid therapy was withdrawn for at least 2 months. Each patient received, at 1-month intervals and in a random order, two single oral doses of DHEA (50 mg and 200 mg) and placebo. During each treatment, urine samples were collected for 24 h, and blood samples were drawn at hourly intervals for 8 h. In patients with pituitary deficiency, plasma DHEA and DHEAS were not detectable and increased, with the 50 mg dose, up to levels observed in young adults. The administration of 200 mg of DHEA induced an increase of both steroids to supraphysiological plasma levels. A small increase of delta 5-androstenediol was observed. In contrast, the increase of plasma delta 4-androstenedione was important and dose dependent. DHEA was also converted into the potent sex steroid testosterone (T). The administration of a 50 mg dose of DHEA restored plasma T to levels similar to those observed in young women. The 200 mg dose induced an important increase of plasma T, slightly below the levels observed in normal men. The increase of plasma dihydrotestosterone levels was small at both doses of DHEA, in contrast with the large conversion of DHEA into androsterone glucuronide and androstanediol glucuronide. Finally, DHEA administration induced a significant and dose dependent increase of plasma estrogens and particularly of estradiol. In conclusion, this short term study demonstrates that: 1) panhypopituitarism is a model of interest to study the metabolism of DHEA; 2) in the absence of pituitary hormones and of adrenal and gonadal steroids, DHEA given orally is mainly converted into delta 4 derivatives, which in turn are strongly metabolized into 5 alpha-3keto-reduced steroids; 3) a significant increase of sex active hormones was observed in plasma after 200 and even 50 mg of DHEA. Thus, biotransformation of DHEA into potent androgens and estrogens may explain several of the reported beneficial actions of this steroid in aging people.

Adult↗
PubMed1997

Increased proliferation of osteoblastic cells expressing the activating Gs alpha mutation in monostotic and polyostotic fibrous dysplasia.

We studied the osteoblastic abnormalities resulting from activating mutation of the Gs alpha gene in two patients with McCune-Albright syndrome and one patient with monostotic fibrous dysplasia. Histomorphometric analysis of dysplastic lesions showed a low number of differentiated osteoblasts along the bone surface and numerous immature alkaline phosphatase-positive mesenchymal cells actively depositing a woven bone matrix. Osteoblastic cells isolated from dysplastic bone lesions expressed a missense mutation in the Gs alpha gene in position 201 and showed increased intracellular basal cyclic adenosine 3',5'-monophosphate levels compared with normal cells isolated from a noninvolved area in the same patient. Cell proliferation evaluated by DNA synthesis was two-fold to threefold greater in osteoblastic cells expressing the mutation compared with normal cells from the same patient and was greater in cells isolated from more severe than less severe fibrotic lesions. In contrast, the synthesis of osteocalcin, a marker of mature osteoblasts, was lower in osteoblastic cells expressing the Gs alpha mutation compared with normal cells from the same patient and was lower in cells isolated from severe compared with less severe fibrotic lesions, indicating that the increased growth in mutated osteoblastic cells was associated with reduced cell differentiation. The results show that activating mutation of Gs alpha in osteoblastic cells leads to constitutive activation of adenylate cyclase, increased cell proliferation, and inappropriate cell differentiation, resulting in overproduction of a disorganized fibrotic bone matrix in polyostotic and monostotic fibrous dysplasia.

Adolescent↗
PubMed1997

[Intra-sellar non-adenomatous expansive process].

More than thirty types of tumors in the sellar region can mimic pituitary adenoma on, magnetic resonance imaging. When they exist, clinical manifestations are not necessarily highly contributive to diagnosis. Headache, visual impairment, signs of antepituitary insufficiency or possible dysmenorrhea with galactorrhea attributed to hyperprolactinemia due to compression of the dopaminergic axis are not specific and may be misleading. Clinical signs of diabetes insipidis and polyphagia are however suggestive of non-pituitary tumors. Consequently, high-resolution imaging (MRI) and sometimes particular diagnostic circumstances (post partum for hypophysitis for example, or breast cancer for metastasis) orient the diagnosis. More rarely tumor enlargement, for example in certain germ cell tumors, provides a clue.

Adolescent↗
PubMed1996

[Medical treatment of pituitary adenoma].

Dopamine agonists are able to restore ovulatory cycles in 80-90% of hyperprolactinemic patients and to reduce tumoral volume (often dramatically) in 80% of macroprolactinomas. Their side-effects will be reduced with the use of parenteral forms or new agonists currently in preparation. Somatostatin analogues administered either subcutaneously by three daily injections (octreotide) or intramusculary with a long-acting formulation every 10-15 days (lanreotide) are able to "normalize" GH levels in 70% of acromegalic patients and to shrink tumor in half of the patients. Side effects are generally minor but an increased incidence of gallstones has been reported. These somatostatin analogs are also very effective in the treatment of TSH-secreting adenomas. Medical treatment of other pituitary adenomas is much more disappointing.

Adenoma↗
PubMed1996

The antigonadotropic activity of progestins (19-nortestosterone and 19-norprogesterone derivatives) is not mediated through the androgen receptor.

To further study the mechanism of the antigonadotropic activity of progestins, the effects of a 19-nortestosterone derivative, norethisterone acetate (NETA), and a 19-norprogesterone derivative, nomegestrol acetate (NOMA), were compared. The aim was to assess whether their action is exerted via the androgen receptor. Ten healthy postmenopausal women were treated for five monthly periods of 24 days separated by 10 days in a randomized cross-over design. Transdermal estradiol, Estraderm TTS (25 micrograms; one patch every 3 days), was given from days 1-24 during the five periods. On the last 12 days, of each estradiol treatment, they all received a placebo, NOMA (5 mg/day), NOMA in association with the nonsteroidal antiandrogen, flutamide (FLU; 250 mg, twice a day), NETA (10 mg/day), or NETA plus FLU. On the other hand, three castrated patients with complete androgen insensitivity (CAI) received NOMA and NETA for two periods of 12 days separated by 3 weeks. In postmenopausal women, the effects of NOMA and NETA on metabolic parameters were studied. Only NETA decreased high density lipoprotein cholesterol. Plasma LH, FSH, and estradiol were measured during each treatment period. A significant decrease in mean plasma LH and FSH levels and their responses to exogenous GnRH was observed with NOMA and NETA treatments compared to placebo (P < 0.001). The pulsatile frequency, but not the amplitude, of LH was significantly decreased during both treatments. Interestingly, the effects of both progestins on gonadotropins were not antagonized by FLU administration. In the patients with CAI, the pulsatile study of gonadotropins was performed before and on day 12 of NOMA and NETA treatments. As in postmenopausal women, both progestins induced similar decreases in LH and FSH. In conclusion, a 19-nortestosterone derivative, NETA, and a 19-norprogesterone derivative, NOMA, have similar antigonadotropic activities. This effect, not antagonized by FLU and observed in patients with CAI, is not mediated via the androgen receptor. The absence of deleterious effects of 19-norprogesterone derivatives on metabolic parameters should favor the therapeutic use of these compounds.

Cholesterol, HDL↗
PubMed1996

Characterization of a monoclonal antibody reacting with the free human luteinizing hormone beta-subunit.

Measurement of serum luteinizing hormone (hLH) is important for the detection and follow-up of patients with pathological processes of the reproductive axis. Detection of the uncombined form of the beta-subunit of hLH, or free hLH beta, has proved to be of clinical interest in the recognition of gonadotroph adenomas. As no monoclonal antibody specific for the free hLH beta is at present available, we elicited monoclonal antibodies using free hLH beta as an immunogen. An antibody, named BLH01, was selected for its specific binding to the free beta-subunit, and its antibody-binding site was characterized at the molecular level, emphasizing the importance of amino acid residues located between the disulfide-bonded Cys93 and Cys100. This region has been demonstrated as being particularly critical for the specific binding of lutropic hormones to their receptors. Topographic assignment of the epitope recognized by BLH01 was then achieved by cross-matching studies based on a library of antibodies directed to hLH beta, and the location of some epitopes on the three-dimensional model of the beta-subunit is proposed. A two-site immunoassay based on BLH01 as capture antibody was then developed. This assay, using BLH01, may constitute a simple, sensitive and highly specific procedure for assessing the clinical usefulness of measuring free hLH beta, particularly for the diagnosis and follow-up of patients presenting with pituitary adenomas.

Adenoma↗
PubMed1996

[Double kidney-total pancreas transplantation with bladder reimplantation. 25 cases].

Twenty five double kidney-pancreas transplantations were performed according to the total pancreas transplantation technique with drainage of exocrine secretions into the bladder via a vesicoduodenostomy. 72% of kidney-pancreas grafts were functional at one year and 59% were functional at four years. The authors observed a slightly higher rejection rate (0.56 versus 0.34) and a higher incidence of urinary tract infection (60% versus 35%) following double pancreas and renal transplantation than after isolated renal transplantation. Complications were rare: two venous thromboses and two cases of urethritis requiring of rediversion of the duodenum into the intestine. These good results, comparable to those reported in the international registry, reflect the value of the pancreatic and renal transplantation technique using a total pancreas drained into the bladder. It would probably be preferable to transplant patients earlier, when chronic renal failure secondary to insulin-dependent diabetes induces end-stage renal failure and the need for haemodialysis.

Adolescent↗
PubMed1995

[Hereditary multiple endocrine neoplasia. New genetic data and clinical applications in type 1 multiple endocrine neoplasia].

Multiple endocrine neoplasia (MEN) is a group of characteristic affections involving benign or malignant secreting tumours of several endocrine glands. Recent progress in genetic mapping has led to the precise localization of the genes causing these familial diseases. This technique provides new means of diagnosis greatly improving conventional diagnostic methods. In type 1 MEN, laboratory tests are directed to identifying the target gland and its effect on hormone status. Imaging techniques including echography, CT scan, magnetic resonance imaging, echoendoscopy and scintigraphy add further information. The molecular genetics approach is an indirect one based on a family study. Blood samples must be obtained from at least two certain probands and at least two healthy members of the family. By mapping the genes with precise genetic probes, the morbid haplotype could be identified and used to predict the risk of morbidity in the descendance. The GENEM 1 (Groupe d'Etudes sur les Néoplasies endocriniennes multiples de type 1) is a multidisciplinary collaboration between endocrine surgeons, endocrinologists, gastroenterologists, geneticians, pathologists and biologists working towards identifying the causal gene and better understand the pathophysiology of these tumours. We are undoubtedly on the threshold of this discovery which could help improve the diagnosis of this generally poorly recognized disease with an underestimated prevalence.

Humans↗
PubMed1995

Pseudo-tumours of the thymus after correction of hypercortisolism in patients with ectopic ACTH syndrome: a report of five cases.

We report the cases of four patients with occult, and one patient with overt, ectopic ACTH syndrome. Cushing's syndrome was cured by removal of the ACTH secreting tumour, op'DDD, ketoconazole or bilateral adrenalectomy. Six to 14 months after remission of hypercortisolism, follow-up computed tomography or magnetic resonance imaging of the thorax revealed in all five patients an anterior mediastinal mass 3-5 cm in length that suggested a thymic carcinoma. Exploratory thoracotomy was performed in four cases and allowed the removal of an enlarged, but normal, thymus. Histological examination revealed no tumour but showed benign thymic hyperplasia with negative immunostaining for ACTH. Thymic enlargement spontaneously disappeared 11 months after its demonstration in the patient who did not undergo thoracotomy. The mechanism of this abnormality is thought to be thymic depletion resulting from high plasma cortisol concentrations followed by 'rebound' thymic hyperplasia when cortisol levels fall. Physicians involved in the management of patients with Cushing's syndrome must be aware of this entity in order to avert a diagnostic thoracotomy.

ACTH Syndrome, Ectopic↗
PubMed1995

Multiple endocrine neoplasia type 1 in France: clinical and genetic studies.

Multiple endocrine neoplasia type 1 (MEN1) is a hereditary syndrome characterized by the involvement of several endocrine glands, including the parathyroid glands, the pancreatic islet cells, the anterior pituitary gland and other neuroendocrine tissues. In order to build up a French MEN1 register, a collaborative network was developed through the 'Groupe d'Etude des Néoplasies Endocriniennes Multiples de type 1' or GENEM 1. A 2-year follow-up in 40 medical and surgical units allowed the identification of more than 150 individual patients and 45 MEN1 families, and defined the major clinical features of the disease in our series. Multiple endocrine neoplasia type 1 is inherited as an autosomal dominant trait. The gene causing this syndrome has been localized to chromosome 11, band 11q13, and molecular genetic markers flanking the MEN1 locus are of use in identifying disease gene carriers in predisposed families. Selected data were presented in order to discuss the management of patients by combined clinical, biochemical and genetic screening. The set-up of a national register by a multi-disciplinary and collaborative medical and surgical network will facilitate further research on the clinical management of MEN1 patients and the basic physio-pathology of the disease.

Adolescent↗