Administration of bovine, porcine and equine growth hormone to the horse: Effect on insulin-like growth factor-1 and selected IGF binding proteins
Journal of Endocrinology v.171, i.1, Oct01

S S de Kock, J P Rodgers, B C Swanepoel and A J Guthrie¹

Abstract

This study investigated the biochemical effects of administration of three types of recombinant growth hormone to the Thoroughbred horse. Either equine or bovine or porcine growth hormone (GH, somatotropin, ST) was administered at a recommended dosage to three to five-year old Thoroughbred geldings, for a period of time up to 21 days. It was shown that in addition to equine GH, bovine and porcine GH were active in the horse, but with the latter presenting injection site reactions which were so serious that administration had to be stopped. The concentrations of a range of growth hormone related serum protein markers were determined prior to, during and following the administration period. Due to the short half-life of GH itself, the objective was to identify GH related markers which show changes in concentration and which could be employed as indicators of the abuse of these hormones. Among the possible markers which were identified, serum total insulin-like growth factor-1 (IGF-1) was shown to be the most promising, increasing to 270% the basal concentration for equine GH administration. Following GH administration IGF-1 took longer to attain baseline concentrations than the time required for GH levels to recover to a normal level. The concentration obtained from the administration significantly exceeded natural levels for IGF-1, as was determined from a population of more than two thousand Thoroughbred horses over three continents. The concentration of serum free IGF-1 as well as IGF binding protein 3 (IGFBP-3) were also shown to be significantly affected by equine and bovine GH.

source; http://journals.endocrinology.org/joe/171/joe1710163.htm 3oct01