The role of the pituitary gland in spontaneous canine mammary tumorigenesis.

The morphological changes of the pituitary gland of 29 female dogs with spontaneous mammary tumours or dysplasia or both were correlated with basal serum prolactin, growth hormone, adrenocorticotrophin, thyrotrophin, cortisol, total cholesterol, thyroxine and thyroid binding index as well as with lesions in other endocrine and genital organs. Spontaneous canine mammary tumorigenesis seemed to be associated with increased secretory activity of growth hormone rather than prolactin cells. Depressed secretory activity of follicle stimulating hormone-, luteinizing hormone- and thyrotrophin-producing cells, as well as signs of inhibition of ovarian (anovulation) and thyroid function, were also consistent findings in dogs with mammary tumours. There also was disturbance in pituitary-adrenal function associated with hyperplastic and neoplastic changes of the pituitary gland and adrenal cortex.