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

Transsphenoidal hypophysectomy normalized GH/IGF-1 but insulin-dependent diabetes persisted postoperatively.

This case report describes a 10-year-5-month-old neutered male Staffordshire Bull Terrier with pituitary somatotroph adenoma causing hypersomatotropism (HS) complicated by insulin-resistant diabetes mellitus. The dog presented with polyuria, polydipsia, progressive inspiratory stridor, and poorly controlled diabetes despite hyperinsulinemia. Diagnostic findings included markedly elevated serum IGF-1 (1,214 ng/mL), confirmed by somatostatin suppression testing. Imaging revealed a pituitary mass with concurrent organomegaly and arthropathy. Transsphenoidal hypophysectomy successfully removed the GH-producing adenoma, with normalization of growth hormone within hours and IGF-1 within one week. Immunohistochemistry confirmed the diagnosis. Despite resolution of hypersomatotropism and improvement in hyperinsulinemia, the dog remained insulin-dependent with persistent diabetes mellitus, eventually requiring euthanasia 9.5 months post-operatively. This case demonstrates that while transsphenoidal hypophysectomy effectively normalizes growth hormone and IGF-1 concentrations in canine pituitary somatotroph adenomas, long-term diabetes management remains challenging and prognosis may be guarded.

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