Which condition is the opposite of Addison's disease regarding cortisol levels?

Cushing's syndrome is characterized by excessively high levels of cortisol in the body, making it the opposite of Addison's disease, which is marked by insufficient production of cortisol. In Addison's disease, the adrenal glands fail to produce adequate amounts of cortisol, leading to symptoms such as fatigue, weight loss, low blood pressure, and increased skin pigmentation. In contrast, Cushing's syndrome results from either excessive production of cortisol due to adrenal tumors, pituitary adenomas, or the administration of glucocorticoid medications. The elevated cortisol levels in Cushing's syndrome cause symptoms like weight gain, high blood pressure, and a characteristic rounding of the face.

Other conditions listed do not primarily involve cortisol levels. Diabetes mellitus relates to issues with insulin and glucose metabolism rather than cortisol levels. Thyroid storm is a hyperthyroid condition leading to increased thyroid hormone levels, and hypoglycemia refers to low blood sugar, which is unrelated to cortisol levels in the same way as Addison's and Cushing's diseases. Thus, Cushing's syndrome is distinctly the condition that presents with high cortisol levels, contrasting the low levels seen in Addison's disease.