What is the pathophysiology of Cushing’s disease?

Cushing’s disease is a specific form of Cushing’s syndrome that is characterized by the excessive secretion of adrenocorticotropic hormone (ACTH) by a benign monoclonal pituitary adenoma.

The excessive secretion of ACTH stimulates the adrenal glands to secrete cortisol, leading to supraphysiological levels of circulating cortisol. The pathophysiology of Cushing’s disease involves several steps:

Formation of a Pituitary Adenoma: The disease begins with the formation of a benign monoclonal pituitary adenoma. This is a tumor that arises from a single cell in the pituitary gland and grows slowly over time.

Overproduction of ACTH: The pituitary adenoma secretes excessive amounts of ACTH. ACTH is a hormone that stimulates the adrenal glands to produce cortisol1.

Overproduction of Cortisol: In response to the high levels of ACTH, the adrenal glands produce excessive amounts of cortisol. Cortisol is a steroid hormone that plays a crucial role in various bodily functions, including the stress response, immune response, and regulation of metabolism.

Effects on the Body: The excessive levels of cortisol in the body lead to the symptoms and complications of Cushing’s disease. These can include obesity, muscle weakness, skin changes, high blood pressure, diabetes, and psychological symptoms.

Negative Feedback Mechanism: Normally, cortisol levels in the body are regulated by a negative feedback mechanism. When cortisol levels are high, the hypothalamus and pituitary gland reduce the production of CRH and ACTH, respectively, which in turn reduces cortisol production. However, in Cushing’s disease, this negative feedback mechanism is disrupted. The pituitary adenoma is not sensitive to high cortisol levels and continues to produce ACTH, leading to persistently high cortisol levels.

The pathophysiology of Cushing’s disease is complex and involves multiple systems in the body. It’s important to note that while the disease is caused by a benign pituitary adenoma, the effects of the excessive cortisol can lead to serious health problems if not treated.