Which of the following clinical findings is NOT associated with Addison's disease?

Addison's disease, a disorder of the adrenal glands, is characterized by insufficient production of adrenal hormones such as cortisol and aldosterone. One of the hallmark features of this condition is an imbalance in electrolytes, particularly the retention and loss of potassium. Patients with Addison's disease often experience hyperkalemia, which is an elevated level of serum potassium. This results from reduced aldosterone, which normally promotes the excretion of potassium by the kidneys.

The other options, such as dehydration, chronic fatigue, and emotional changes, are indeed associated with Addison's disease. Dehydration can occur due to aldosterone deficiency, leading to a loss of sodium and consequent fluid loss. Chronic fatigue is a common symptom because of low cortisol levels, which impact energy metabolism. Emotional changes, including depression and irritability, can also arise from hormonal imbalances and the stress of dealing with chronic illness.

Thus, the finding of decreased serum potassium is not consistent with what is typically observed in Addison's disease, making it the correct answer to the question.