Pituitary adenomas are frequently associated with one of two common diseases in dogs; pituitary-dependent hyperadrenocorticism and central diabetes insipidus. These tumors may be small (micradenomas) or sufficently large to cause a mass-effect (macroadenomas) with secondary thalamic disease such as Frohlich's adiposogenital syndrome.
Clinically affected dogs present with non-neurological symptoms of weight loss, polyuria, polydipsia and lethargy. Other, more specific symptoms, are referable to individual disease states. For example, symptoms associated with hyperadrenocroticism due to pituitary adenoma include polyphagia, polyuria, polydipsia, dermatopathy, distinctive 'potbelly' appearance and symmetrical alopecia.
Neurological signs due to cranial compression due to mass-effect are extremely rare and are usually associated with pituitary adenocarcinomas. However, pressure on the optic chiasma may induce ocular changes.
Diagnosis is difficult as imaging with CT or MRI may not reveal a mass within the sella turcica, requiring hypophyseal biopsy or exploratory craniotomy.
Definitive diagnosis usually requires intraoperative or postmortem biopsy, verifying adenomatous changes to the pituitary gland.
A differential diagnosis would include lymphoma, hypothalamic-pituitary trauma, dorsally expanding cysts, inflammatory granuloma, lymphocytic hypophysitis, congenital malformations such as empty sella syndrome and neoplasms such as infundibuloma, xanthogranuloma, craniopharyngioma, pituitary adenocarcinoma and metastatic tumors such as metastatic mammary carcinoma, lymphoma, malignant melanoma and pancreatic carcinoma.
- Vet Path
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