Normal function of the hypothalamic-pituitary growth axis in three dwarf Friesian foals

Serial blood samples were collected from three dwarf Friesian foals to examine their endogenous growth hormone (GH) profiles, and the integrity of the GH-insulin-like growth factor-I (IGF-I) axis was tested in one of them by examining its responses to the administration of GH-releasing hormone (GHRH) and to 10 days of treatment with recombinant equine GH. The basal serum concentrations of IGF-I in the three dwarf foals were compared with those in nine age-matched normal foals. All the dwarf foals secreted endogenous GH. Stimulation with 7.0 mu g/kg GHRH led to a 1400 per cent increase in plasma GH concentration in the dwarf foal tested, and 10 daily subcutaneous treatments with 20 mu g/kg recombinant equine GH led to a 100 per cent increase in its serum IGF-I concentration. The basal serum concentrations of IGF-I in the dwarf foals were not significantly different from those of the normal foals.