title: Short-term effect of ovariectomy on measures of insulin sensitivity and response to dexamethasone administration in horses.
abstract: OBJECTIVE
  To evaluate the effect of ovariectomy on insulin sensitivity in horses and determine whether the effects of suppression of the hypothalamo-pituitary-adrenal axis differ before and after ovariectomy.
  
  
  METHODS
  6 healthy mares.
  
  
  METHODS
  The horses underwent an IV glucose tolerance test (IVGTT), an insulin sensitivity test, and a dexamethasone suppression test before and 5 weeks after ovariectomy. Body weight, serum cortisol and plasma ACTH concentrations, serum insulin-to-blood glucose concentration ratios, and changes in blood glucose concentration with time after injection of glucose or insulin were compared before and after ovariectomy.
  
  
  RESULTS
  The dexamethasone injection resulted in a decrease in serum cortisol concentration before and after ovariectomy. In all horses, baseline plasma ACTH concentrations were within the reference range before and after ovariectomy. For each mare, results of an IVGTT before and after ovariectomy were considered normal. No significant differences in basal blood glucose concentration or time to reach baseline glucose concentration after an IVGTT were observed. Basal serum insulin concentration and serum insulin-to-blood glucose concentration ratios were not significantly different before or after ovariectomy, nor was the mean time to attain a 50% decrease in blood glucose concentration after insulin injection.
  
  
  CONCLUSIONS
  Results indicated that ovariectomy does not appear to modify dexamethasone response in horses and that it does not modify short-term measures of insulin sensitivity. Findings suggested that horses undergoing ovariectomy are not at higher risk of developing equine metabolic syndrome or hypothalamo-pituitary-adrenal axis dysfunction and associated morbidity.
authors.affiliation: Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Purdue University, West Lafayette, IN 47907.
authors.forename: François R
authors.initials: FR
authors.lastname: Bertin
authors.forename: Karine S
authors.initials: KS
authors.lastname: Pader
authors.forename: Timothy B
authors.initials: TB
authors.lastname: Lescun
authors.forename: Janice E
authors.initials: JE
authors.lastname: Sojka-Kritchevsky
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D003907:Dexamethasone / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D005951:Glucose Tolerance Test / Q000662:veterinary; D006736:Horses / Q000378:metabolism*; D006854:Hydrocortisone / Q000097:blood; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects*; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000502:physiology*; D010052:Ovariectomy / Q000009:adverse effects / Q000662:veterinary*; D010913:Pituitary-Adrenal System / Q000187:drug effects*
chemical_list: D001786:Blood Glucose; D007328:Insulin; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone