Cushing's syndrome results from prolonged elevations in glucocorticoids in the body. Glucocorticoids are steroid hormones that affect the metabolism of glucose. A person with Cushing's syndrome has a chronic elevation of glucose in the blood that increases the risk for insulin resistance and diabetes. Fatty liver, or steatosis, is a common indicator for insulin resistance.
Fatty Liver
The amount of fatty acid in the liver is the difference between the amount of fat coming into the liver and the amount of fat excreted from the liver. When your body is resistant to insulin, it cannot metabolize glucose efficiently and therefore seeks alternative sources of energy such as fats and proteins. Increased breakdown and release of fat from tissue, increases the amount of fat delivered to the liver. A person with Cushing's syndrome will likely develop insulin resistance, thereby increasing fat accumulation in the liver.
Cortisol Regulation
Cortisol secretion is controlled by the negative feedback inhibition of HPA axis, or hypothalamic-pituitary-adrenal axis. The signal for cortisol secretion begins with the hypothalamic release of CRH, or corticotropin-releasing hormone. CRH then stimulates cells of the anterior pituitary gland to release ACTH, or adrenocorticotropic hormone. ACTH stimulates the adrenal cortex to increase cortisol synthesis. The HPA axis is inhibited when cortisol concentrations are higher than normal.
Causes of Cushing's Syndrome
Cushing's syndrome is most commonly caused by high-dose corticosteroid use. It may also be caused by an increased secretion of ACTH from pituitary tumor or cancer of the lung. An adrenal tumor that releases uncontrolled amounts of cortisol also causes Cushing's syndrome.
Clinical Presentation
A person with Cushing's syndrome may experience physical changes that include red cheeks, moonlike face, a buffalo hump, purple striations or streaks along the belly, and pouching of the belly. There may also be muscle weakness, tendency to bruise easily, high blood pressure, bone density loss or weakening of the bones, diabetes, and increased risk for infections.
References
- "European Journal of Endocrinology"; Hepatic Steatosis in Cushing's Syndrome; A.G. Rockall, et al.; December 2003
- "Harrison's Principles of Internal Medicine"; Dennis Kasper, M.D., et al.; 2004
- MayoClinic.com: Cushing's Syndrome
