Case Report: Treatment of hypersomatotropism in a diabetic dog with transsphenoidal hypophysectomy

Background Pituitary somatotroph adenoma is rare in dogs and may cause hypersomatotropism (HS) leading to insulin resistance and diabetes mellitus (DM). Case description A 10-year-5-month-old neutered male Staffordshire Bull Terrier presented with polyuria, polydipsia, progressive inspiratory stridor, and poorly controlled DM with hyperinsulinemia and insulin resistance. Serum insulin-like growth factor (IGF-1) was markedly elevated (1,214 ng/mL; reference interval, 42–449 ng/mL) and suggested HS which was further supported by a somatostatin suppression test. Magnetic resonance and computed tomography (CT) imaging revealed a pituitary mass, organomegaly, and arthropathy. Treatment and outcome The pituitary mass was removed by transsphenoidal hypophysectomy. Immunohistochemistry confirmed a growth hormone (GH)-producing pituitary adenoma. Postoperatively, GH normalized within hours, and IGF-1 values within a week. 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. Conclusion 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.