Although HS resolved and hyperinsulinemia improved postoperatively, the dog remained dependent on insulin and DM persisted which eventually led to euthanasia of the dog about 9 and a half months post-operatively.<h4>Conclusion</h4>Transsphenoidal hypophysectomy was effective in normalization of GH and IGF-1 concentrations in a dog diagnosed with a pituitary somatotroph adenoma but the postoperative course was characterized by persistent insulin dependency and DM. This evidence concerns the gene GH1 and diabetes mellitus.