title: Thyroid function and pregnancy status in broodmares.
abstract: OBJECTIVE
  To determine whether thyroid function was associated with pregnancy status in broodmares.
  
  
  METHODS
  Prospective study.
  
  
  METHODS
  79 Thoroughbred and Standardbred broodmares between 2 and 22 years old.
  
  
  METHODS
  Serum triiodothyronine (T3) concentration was measured before and 2 hours after i.v. administration of thyrotropin releasing hormone (TRH), and serum thyroxine (T4) concentration was measured before and 4 hours after TRH administration. Pregnancy status was monitored by means of transrectal ultrasonography beginning 16 days after ovulation.
  
  
  RESULTS
  Baseline T3 and T4 concentrations varied widely. In all mares, serumT3 concentration increased in response to TRH administration. Serum T4 concentration increased in response toTRH administration in all but 2 mares. Pregnancy rate was 76%. Baseline and stimulated serum T3 and T4 concentrations were not significantly different between mares that became pregnant and those that did not.
  
  
  CONCLUSIONS
  Results suggest that decreased thyroid function is uncommon in mares and poor thyroid function is not a common cause of infertility. Thus, the practice of indiscriminately treating broodmares with thyroid hormone to enhance fertility appears questionable at this time.
authors.affiliation: Section of Reproduction, Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA 19348, USA.
authors.forename: Travis B
authors.initials: TB
authors.lastname: Meredith
authors.forename: Ina
authors.initials: I
authors.lastname: Dobrinski
mesh_terms: D000818:Animals; D005260:Female; D006736:Horses / Q000097:blood / Q000502:physiology*; D010060:Ovulation; D011247:Pregnancy; D018873:Pregnancy Rate; D011270:Pregnancy, Animal / Q000097:blood / Q000187:drug effects / Q000502:physiology*; D011446:Prospective Studies; D013961:Thyroid Gland / Q000502:physiology*; D013973:Thyrotropin-Releasing Hormone / Q000008:administration & dosage*; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
chemical_list: D014284:Triiodothyronine; D013973:Thyrotropin-Releasing Hormone; D013974:Thyroxine