BHA clarifies use of levothyroxine sodium
Levothyroxine sodium must not be present in the horses system on raceday.
The British Horseracing Authority (BHA) has issued a notice clarifying whether, when and how levothyroxine sodium may be administered under the BHA Rules of Racing.
Levothyroxine sodium is a prohibited substance and therefore must not be present in the horses system on raceday. It is a synthetic version of the naturally occurring hormone, thyroxine, that is made and released by the thyroid gland.
The BHA's rule on the use of veterinary treatment and medication states that “every treatment must be fully justifiable by the medical condition of the horse receiving the treatment”.
For the administration of the hormone to be justified, the organisation say that the horse must have undergone dynamic endocrine tests, which show good evidence of either equine metabolic syndrome or hypothyroidism.
The BSAVA has opened submissions for the BSAVA Clinical Research Abstracts 2026.
