What causes Cushing's syndrome?

Cushing's syndrome is primarily caused by prolonged exposure to elevated levels of glucocorticoids, which are steroid hormones that play a vital role in various bodily functions, including metabolism, immune response, and stress regulation. These elevated levels can come from endogenous sources, meaning they are produced by the body itself, often due to an adrenal tumor or pituitary gland disorder that leads to excessive production of adrenocorticotropic hormone (ACTH), which in turn stimulates the adrenal glands to produce more cortisol.

This condition manifests with a variety of symptoms, including weight gain, a rounded face, increased fat around the neck, thinning skin, and easy bruising, among others. The underlying mechanism revolves around the disruption of the body’s hormonal balance caused by these elevated glucocorticoids.

The other options represent conditions that are not characteristic of Cushing's syndrome. Increased physical activity typically does not lead to the hormonal imbalances seen in Cushing's, while low cortisol levels and a deficiency of glucocorticoids are associated with conditions such as Addison's disease, rather than the excess seen in Cushing's syndrome. Understanding the distinction between these conditions is crucial for diagnosis and treatment in clinical practice.