Which of the following is a key symptom of adrenal insufficiency?

Fatigue is a key symptom of adrenal insufficiency because the adrenal glands produce hormones, including cortisol, which play a crucial role in regulating metabolism, stress response, and energy levels. In cases of adrenal insufficiency, the body does not produce enough cortisol, leading to a significant decline in energy and an overwhelming sense of tiredness. Patients often report feeling fatigued even after adequate rest, as their bodies struggle to manage energy production and maintain homeostasis without sufficient cortisol levels.

In contrast, increased appetite and weight gain are not typically associated with adrenal insufficiency. In fact, patients may experience weight loss or difficulty maintaining weight due to metabolic imbalances. High heart rate is also not a common feature of adrenal insufficiency; instead, patients might experience other cardiovascular symptoms related to low blood pressure and electrolyte imbalances. Thus, the presence of fatigue stands out as a distinctive and telling sign of this condition.