EXPRESS: Presumed Partial Aplasia of the Hypothalamus and Pituitary Gland Causing Central Diabetes Insipidus in an Adult Cat

Case series summary A 2-year-old neutered male domestic shorthair cat presented with severe lethargy, hyporexia, dehydration, and poor body condition. The incidence of polyuria/polydipsia was unknown because of the presence of multiple other cats in the household. Laboratory findings revealed severe hypernatremia, isosthenuria, hemoconcentration, and moderate azotemia. MRI of the head demonstrated partial hypoplasia/aplasia of the hypothalamus and pituitary gland, confirming congenital central diabetes insipidus; additional endocrine testing excluded other causes. Initial fluid therapy improved azotemia and stabilized the hematocrit, but hypernatremia persisted until desmopressin therapy was initiated. The cat was successfully managed long-term with gradually titrated oral desmopressin, achieving normalization of electrolytes. Relevance and novel information This report details the first documented case of central diabetes insipidus in an adult cat, attributed to presumed partial aplasia of the hypothalamus and pituitary gland, with no other hormonal deficiencies.