Adrenocorticotropin-containing neoplastic cells in a pars intermedia adenoma in a horse
Horvath, C.J.; Ames, T.R.; Metz, A.L.; Larson, V.L.
Journal of the American Veterinary Medical Association 192(3): 367-371
1988
ISSN/ISBN: 0003-1488 PMID: 2833479 Document Number: 320356
Pituitary-dependent hyperadrenocorticism was diagnosed in a 14-year-old Arabian mare with chronic weight loss, hirsutism, polyuria, and polydipsia. The mare had a lymphopenia, a mature neutrophilia and an eosinopenia, glucosuria and consistent hyperglycaemia. Plasma glucose concentrations were resistant to suppression by insulin. Plasma cortisol concentrations were within normal limits, but did not respond to dexamethasone suppression and had an exaggerated response to ACTH stimulation. PM examination revealed a chromophobe adenoma of the pars intermedia of the pituitary gland. The zona fasciculata of the adrenal cortex and the pancreatic islets of Langerhans were hypertrophied. An immunohistological staining technique was used to demonstrate ACTH-containing neoplastic cells in the pituitary mass. These cells released ACTH and other peptides that initiated the chain of endocrinological events leading to clinical disease.