Immunocytochemical study of the hypophysis in 25 dogs with pituitary-dependent hyperadrenocorticism

Abstract

Abstract. Pituitary adenomas were found in 21 (84%) of 25 dogs with spontaneous pituitary-dependent hyperadrenocorticism. Six dogs had pars intermedia adenomas, whereas 15 had tumours of the pars distalis. Diffuse corticotroph cell hyperplasia was found in 1 of the 4 pituitaries without adenoma; in 2 dogs with pituitary adenoma, coexisting hyperplasia of the surrounding corticotrophs was also present. Immunocytochemical staining of the pituitaries revealed positive staining for ACTH, β-lipotrophin, and β-endorphin in the majority of both pars distalis and pars intermedia adenomas. The most frequent and intense staining was found with anti-β-endorphin. In most part intermedia tumours, many cells stained strongly for α-MSH; double immunostaining of one pars intermedia adenoma for ACTH and α-MSH showed that some tumour cells stained only for ACTH or α-MSH whereas others contained both peptides. Only occasional cells stained for α-MSH in pars distalis adenomas.