Endogenous hypercortisolism occurs in approximately 1 to 2.5 per 1000 dogs per year (Willeberg and Priester 1982; O’Neill et al. 2016), and is most frequently (~80–85%) caused by an ACTH-producing pituitary adenoma (pituitary-dependent hypercortisolism; PDH) (Galac et al. 2010c). The gene discussed is POMC; the disease is pyruvate dehydrogenase deficiency.