title: Thyroid function in anhidrotic horses.
abstract: BACKGROUND
  This study was performed to determine whether anhidrotic horses have altered thyroid function compared with horses that sweat normally.
  
  
  OBJECTIVE
  Anhidrotic horses have normal thyroid function.
  
  
  METHODS
  Ten client-owned horses with clinical signs of anhidrosis were paired with 10 horses living in the same environment that had normal sweat production.
  
  
  METHODS
  Horses were diagnosed as having normal sweat production or being anhidrotic based on responses to intradermal injections of terbutaline and physiologic responses to lunging exercise. Control horses were selected from the same environment and matched as closely as possible to anhidrotic horses in terms of age, sex, breed, and athletic condition. Thyrotropin-releasing hormone (TRH) stimulation tests were performed in both horses at the same time, once in the summer or fall, and once again in winter.
  
  
  RESULTS
  Anhidrotic horses produced less sweat in response to intradermal injections of terbutaline and exercise than did control horses. They also had greater increases in body temperature and respiratory rate in response to exercise. Resting concentrations of thyroid hormones and thyroid-stimulating hormone (TSH) were not different between anhidrotic and control horses. Thyroid hormone responses to TRH also were not different between the 2 groups of horses. However, anhidrotic horses had a significantly different TSH response to TRH compared with control horses, particularly in the winter.
  
  
  CONCLUSIONS
  The biologic relevance of the altered TSH response to TRH in anhidrotic horses is uncertain, considering that TSH concentrations remained within previously reported normal ranges and thyroid hormone responses were not different between anhidrotic and control horses.
authors.affiliation: Department of Clinical Sciences, North Carolina State University, Raleigh, NC, USA. quiksilvr@bellsouth.net
authors.forename: B A
authors.initials: BA
authors.lastname: Breuhaus
mesh_terms: D000818:Animals; D006734:Horse Diseases / Q000097:blood*; D006736:Horses; D007007:Hypohidrosis / Q000097:blood / Q000662:veterinary*; D005082:Physical Exertion; D012621:Seasons; D013959:Thyroid Diseases / Q000097:blood / Q000662:veterinary*; D013972:Thyrotropin / Q000097:blood / Q000378:metabolism; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology; D013974:Thyroxine / Q000378:metabolism
chemical_list: D013973:Thyrotropin-Releasing Hormone; D013972:Thyrotropin; D013974:Thyroxine