Hypothalamic corticotrophin releasing factor activity in dogs with pituitary-dependent hyperadrenocorticism

Hypothalamic corticotrophin releasing factor (CRF) activity was determined in five dogs with spontaneous hyperadrenocorticism and in three control animals (one untreated, one treated with high doses of ACTH for 2 months and one treated with high doses of cortisone for 2 months). Hypothalamic CRF activity was low or undetectable in four dogs with Cushing's syndrome due to an adrenocortical tumour. The results are compatible with a pituitary origin for pituitary-dependent hyperadrenocorticism in the dog but are not conclusive; direct information about the rates of hypothalamic CRF secretion is required.