What medical condition is usually linked to low levels of cortisol?

Low levels of cortisol are primarily associated with Addison’s disease, which is an adrenal insufficiency. In this condition, the adrenal glands do not produce sufficient amounts of cortisol and often aldosterone, leading to a variety of symptoms, including fatigue, weight loss, low blood pressure, and increased skin pigmentation.

Addison's disease can result from autoimmune destruction of the adrenal glands, infections, or other conditions affecting adrenal function. The hallmark of this condition is indeed the deficiency of cortisol, which is crucial for various metabolic processes, managing stress responses, and regulating blood sugar levels.

In contrast, other conditions listed are associated with different hormonal imbalances. Cushing's syndrome, for instance, is characterized by excess cortisol production, often leading to symptoms such as weight gain, easy bruising, and high blood pressure. Graves’ disease and thyrotoxicosis relate to excess thyroid hormone production rather than cortisol levels.