Which condition is characterized by elevated levels of cortisol in the blood?

Cushing's syndrome is characterized by elevated levels of cortisol in the blood. This condition can result from various causes, such as a pituitary adenoma that secretes adrenocorticotropic hormone (ACTH), adrenal tumors, or ectopic ACTH production. The excess cortisol leads to a range of symptoms, including weight gain, hypertension, glucose intolerance, and distinctive changes in fat distribution, such as a rounded face and abdominal obesity.

Graves' disease primarily affects the thyroid gland, leading to hyperthyroidism rather than changes in cortisol levels. Addison's disease is associated with an underproduction of adrenal hormones, including cortisol, leading to symptoms like fatigue, weight loss, and hyperpigmentation. Diabetes mellitus involves issues with insulin regulation and glucose metabolism, not cortisol levels. Thus, Cushing's syndrome is the correct answer as it is directly linked to elevated cortisol levels in the bloodstream.