Juvenile Addison's Disease JADD (hypoadrenocorticism) occurs when the adrenal glands stop secreting the natural steroid hormones (glucocorticoid) and hormones (mineralocorticoids) necessary for the regulation of sodium and potassium levels in the blood. Addison?s disease can occur in any breed of dog and it has an average age of onset of 4 years. With Juvenile onset, the average age of puppies affected with JADD is 5 months; however, puppies as young as 8 weeks and as old as 12 months of age have been identified. Addison?s disease is diagnosed by a veterinarian using a blood test called an ACTH stimulation test. The clinical signs of Addison?s disease can include lethargy, lack of appetite, vomiting and diarrhea. This form of the disease is inherited as an autosomal recessive disease meaning that affected puppies inherited one mutant copy of this gene from each of their parents. In addition, JADD is not completely penetrant meaning that not all puppies with two copies of the mutation will go on to develop the disease. [compiled from information via OFA, and UC Davis website]