The study found that Addison’s Disease (AD), the late-onset failure of adrenal gland function, is clearly inherited and appears to be regulated by a single gene that is inherited as an autosomal recessive. Researchers collected DNA samples and pedigrees from 390 Bearded Collies, 533 Standard Poodles and 167 Leonbergers. The samples were from both affected and non-affected dogs. Not enough affected Leonbergers were found, so research could not be completed for this breed. Researchers found that AD equally affects males and females; contrary to the bias in the literature, which stated that females were primarily affected. They also found that the coat color of the dog was not relevant. This study has provided the basis for an important next step: scientists will start screening DNA for a genetic marker. Once that marker is found, a DNA test to determine carriers for the disease can be developed.