Steroid Profiles in the Diagnosis of Canine Adrenal Disorders

INTRODUCTION Diagnosis of adrenal disease in domestic animals usually is dependent on the manipulation of the hypothalamo-pituitary-adrenal axis (HPA) and the measurement of cortisol (i.e., ACTH stim test; low dose dexamethasone suppression (LDDS) test; urine cortisol/creatinine ratio test; or the combined dexamethasone suppression/ACTH stimulation test). More recently, other steroid measurements have been utilized to evaluate the HPA, including steroid hormone profiles1,2, and 17-hydroxyprogesterone,3-5 which have revealed that suspected adrenal disease conditions may be caused by steroids other than cortisol (or in addition to cortisol).3 Determination of pituitary-dependent hyperadrenocorticism (PDH), or adrenal-dependent hyperadrenocorticism (ADH), is now usually made by evaluation of the 4-hour timepoint of the LDDS test6, by endogenous ACTH measurement,7 or by ultrasound visualization of the adrenal glands.7,8 Hyperadrenocorticism (HAC) is defined as an overproduction of steroid hormones by the adrenal cortex.4 Cushing’s syndrome refers to all causes of hyperadrenocorticism with excess production of cortisol,6 while atypical Cushing’s disease refers to hyperadrenocorticism caused by increased levels of intermediate adrenal steroids that frequently are referred to as “sex steroids”.9