Home
http://www.virbac.fr/ http://www.boehringer-ingelheim.com/ http://www.novartis.com/ http://www.animalhealth.bayerhealthcare.com/
vetcontact
Vetrinär
Tiermedizin
  WELCOME  
vetcontact
Vetrinär
Tiermedizin
  Home  
  Login / Newsletter  
vetcontact
Vetrinär
Tiermedizin
  CONTACTS  
vetcontact
Vetrinär
Tiermedizin
  Classifieds  
  New Products  
  VetCompanies  
  VetSchools  
vetcontact
Vetrinär
Tiermedizin
  PROFESSION  
vetcontact
Vetrinär
Tiermedizin
  Edutainment  
  VetAgenda  
  Presentations  
  Posters  
  ESAVS  
  Specialisation  
vetcontact
Vetrinär
Tiermedizin
  INSIGHT  
vetcontact
Vetrinär
Tiermedizin
  Congress News  
  Picture Galleries  
vetcontact
Vetrinär
Tiermedizin
  PRODUCTS  
vetcontact
Vetrinär
Tiermedizin
  Bayer  
  Boehringer Ing.  
  Novartis  
  Virbac

 
  Simply book for less...  
    

Bovine    Equine    Small Animal Practice    Swine Practice    Articles    Vetjournal    
deutsch english español polski francais
Home / WELCOME / Archiv / Small Animal Practice /     
 
Ectopic secretion of GHRH
Growth hormone-releasing hormone (GHRH) is normally secreted in the hypothalamus. This excellent article describes diagnosis and treatment of neuroendocrine tumors in the hypothalamus, leading to excessive production of GHRH. Very interesting!

The aim of this article is to briefly review the physiology of and the diagnosis and treatment of GHRH-mediated acromegaly. Moreover, the role of GHRH and its antagonists in the pathogenesis and treatment of cancer will be reviewed.

Hypothalamic GHRH is secreted into the portal system, binds to specific surface receptors of the somatotroph cell and elicits intracellular signals that modulate pituitary GH synthesis and/or secretion.

GHRH-producing neurons have been well characterized in the hypothalamus by immunostaining techniques.
Hypothalamic tumors, including hamartomas. choristomas, gliomas. and gangliocitomas. may produce excessive GHRH with subsequent GH hypersecretion and resultant acromegaly.

GHRH is synthesized and expressed in multiple extrapituitary tissues.
Excessive peripheral production of GHRH by a tumor source would therefore be expected to cause somatotroph cell hyperstimulation and increased GH secretion.

The structure of hypothalamic GHRH was infact elucidated from material extracted from pancreatic GHRH-secreting tumors in two patients with acromegaly.

Immunoreactive GHRH is present in several tumors, including carcinoid tumors, pancreatic cell tumors, small-cell lung cancers, adrenal adenomas, and pheochromocitomas which have been reported to secrete GHRH. Acromegaly in these patients. however, is uncommon.

In a retrospective survey of 177 acromegalic patients only a single patient was identified with elevated plasma GHRH levels.
Measuring GHRH plasma levels therefore provides a precise and cost-effective test for the diagnosis of ectopic acromegaly.
Peripheral GHRH levels are not elevated in patients with hypothalamic GHRH- secreting tumors, supporting the notion that excess eutopic hypothalamic GHRH secretion into the hypophyseal portal system does not appreciably enter the systemic circulation.

Elevated circulating GHRH levels, a normal or small-size pituitary gland, or clinical and biochemical features of other tumors known to be associated with extrapituitary acromegaly, are all indications for extrapituitary imaging.

An enlarged pituitary is, however, often found on MRI of patients with peripheral GHRH-secreting tumors, and the radiologic diagnosis of a pituitary adenoma may be difficult to exclude.

Surgical resection of the tumor secreting ectopic GHRH should reverse the hypersecretion of GH, and pituitary surgery should not be necessary in these patients. Nonresectable, disseminated or reccurrent carcinoid syndrome with ectopic GHRH secretion can also be managed medically with long-acting somatostatin analogs (octreotide and lanreotide).

The presence of GHRH and its receptors in several extrahypothalamic tissues, including ovary, testis and the digestive tract, suggests that GHRH may have a regulatory role in these tissues.

As previously mentioned, biologically or immunologically active GHRH and mRNA encoding GHRH have been found in several human malignant tumors. including cancers of the breast, endometrium and ovary and their cell lines.

The synthesis and evaluation of analogs with various modifications revealed that certain hydrophobic and helix-stabilizing amino acid substitutions can produce antagonists with increased GH releasing inhibitory potencies and GHRH receptor-binding affinities in vitro.

The review of experimental results of these substances are promising altrough no clinical data are yet available.

Finally, the advent of these antagonists has allowed significant progress in the understanding of the role of the central and tissue GHRH-GH-IGFs system in the pathogenesis of tumors.


Source: Doga M, Bonadonna S, Burattin A, Giustina A. (2001): Ectopic secretion of growth hormone-releasing hormone (GHRH) in neuroendocrine tumors: relevant clinical aspects. In: Ann Oncol. 2001;12 Suppl 2:S89-94.




Tell a friend   |   Print version   |   Send this article

SMALL ANIMAL PRACTICE

Patient-specific facemask to facilitate brain biopsymembers
The objective of this pilot study was to describe the application and first preliminary data of a novel MRI and CT compatible patient-specific facemask for stereotactic brain biopsy of intracranial lesions in dogs. Five client-owned dogs presenting for neurological deficits consistent with forebrain disease were included in the study. All dogs had MRI findings consistent with an intracranial lesion. But biopsies in this region are not easy to obtain. Does an individual face mask help?

  • RET-He to diagnose iron-deficient erythropoiesis in dogsmembers
  • Hypertriglyceridemia-Associated Proteinuria in Miniature Schnauzersmembers
  • Gastrointestinal dysmotility disorders in critically ill animalsmembers
  • Disorder of sex development in a cat with chromosome mosaicism members
  • Generalized discoid lupus erythematosus in dogs members
  • Epidermolysis bullosa acquisita in dogsmembers
  • Chiari-Like Malformation and Syringomyelia in American Brussels Griffon Dogsmembers
  • Efficacy and Potential Complications of Transjugular Liver Biopsymembers
  • Hypomagnesemia in Brachycephalic Dogsmembers
  • Comparison of two minimally invasive techniques for liver biopsy members
  • Topical aqueous sirolimus and the tear production members
  • JAK 1/2 inhibitor in the treatment of canine B-cell lymphomamembers


  • [ Home ] [ About ] [ Contact / Request ][ Disclaimer ]

    Copyright © 2001-2016 VetContact GmbH
    All rights reserved