Hypoadrenocorticism: This disease results from the adrenal gland not producing enough adrenal hormones. Symptoms include vomiting, a poor appetite, and lethargy. Due to the vagueness of the symptoms, Addison’s disease can be mistaken for other illnesses, and diagnosis can be difficult until it reaches more advanced stages. Severe symptoms include acute shock and death and happen when potassium levels are so high it affects heart function or when the dog is stressed. Your vet can confirm the diagnosis through a series of tests.