Which symptom is most indicative of Addison's disease?

Fatigue is the most indicative symptom of Addison's disease due to the adrenal glands' inability to produce sufficient amounts of cortisol, a crucial hormone for energy regulation and stress response. Patients with Addison's disease often experience chronic fatigue as their bodies struggle to maintain normal physiological functions without adequate cortisol levels. This fatigue can result from a combination of hormonal imbalance, electrolyte disturbances, and the overall lack of energy that accompanies adrenal insufficiency.

In contrast, weight gain is typically associated with conditions like Cushing's syndrome due to elevated cortisol levels, while hirsutism is linked to excess androgen production, often seen in polycystic ovary syndrome or adrenal tumors. Increased energy would be contrary to the effects of hormone deficiency found in Addison's disease, as patients tend to have low energy levels. Thus, fatigue emerges as the key symptom that points toward Addison's disease, highlighting the impact of insufficient adrenal function on overall well-being.