Thyroid function and pregnancy status in broodmares.
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.
Meredith
Travis B
TB
Section of Reproduction, Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA 19348, USA.
Dobrinski
Ina
I
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
D014284:Triiodothyronine; D013973:Thyrotropin-Releasing Hormone; D013974:Thyroxine