ISSN 2398-2977      

Endocrine: combined dexamethasone suppression / TRH stimulation test

pequis

Synonym(s): Combined dexamethasone suppression / thyrotropin releasing hormone stimulation test


Overview

  • Dynamic suppression of cortisol levels by dexamethasone; TRH stimulation over-rides dexamethasone suppression in horses with pars pituitary intermedia dysfunction (PPID) Pituitary pars intermedia dysfunction (PPID), but not in healthy horses.
  • Initial reports indicated this combined testing protocol may be a more powerful tool for diagnosis of PPID Pituitary pars intermedia dysfunction (PPID) than either test alone, but it has been superseded by more reliable and straightforward tests.
  • It is unlikely to offer any advantage over the dexamethasone suppression test. The TRH stimulation tests using ACTH rather than cortisol is preferred.
  • Do not perform between August and October.

Sampling

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Tests

Methodologies

  • Radioimmunoassay.
  • Chemiluminescence.
  • Method determines required specimen type (plasma or serum).

Availability

  • Most veterinary commercial, reference and university laboratories.

Validity

Sensitivity

  • 88%.

Specificity

  • 76%
  • PPV: 71%.
  • NPV: 90%.

Technique (intrinsic) limitations

  • Interpret in conjunction with clinical signs and results of other testing.
  • Figures above for sensitivity, specificity, NPV and PPV may be misleading as they did not take into account seasonality.

Result Data

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Frank N et al (2006) Evaluation of the combined dexamethasone suppression/thyrotropin-releasing hormone stimulation test for detection of pars intermedia pituitary adenomas in horses. J Vet Intern Med 20 (4), 987-993 PubMed.
  • Eiler H et al (1997) Results of a combined dexamethasone suppression/thyrotropin-releasing hormone stimulation. Test in healthy horses and horses suspected to have a pars intermedia pituitary adenoma. JAVMA 21 (1), 79-81 PubMed.

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