If you exclude cases caused by medication (as mentioned earlier), about 4 in 5 cases of Cushing's syndrome are caused by a pituitary adenoma. The abnormal cells in the adenoma are not 'turned down' by feedback from the high levels of cortisol. The ACTH stimulates the adrenal glands which then make too much cortisol. It is usually less than 1 cm in size and is made of abnormal cells which make lots of ACTH. These include the following: Pituitary adenoma - Cushing's diseaseĪ pituitary adenoma is a small, non-cancerous (benign) tumour in the pituitary gland.
So, the level of cortisol is kept within a certain range - just enough as is needed by the body.
This means that the adrenal gland is then stimulated less and therefore less cortisol is made. That is, as the level of cortisol in the bloodstream rises above a certain level, it turns down the amount of ACTH made by the pituitary gland. However, cortisol has what is known as a negative feedback effect on the pituitary gland. If the level of ACTH increases in the bloodstream, the adrenal glands make more cortisol. CRH stimulates certain cells in the pituitary gland to make ACTH.ĪCTH passes into the bloodstream, is carried to the adrenal glands and stimulates the adrenal gland to make cortisol. CRH is made in a small part of the brain called the hypothalamus, which is just above the pituitary gland. The amount of ACTH made by the pituitary gland is largely controlled by another hormone called corticotropin-releasing hormone (CRH). It makes several hormones, including ACTH. The pituitary gland lies just below the brain. The amount of cortisol which is made in the adrenal glands is controlled by another hormone called adrenocorticotropic hormone (ACTH) - and sometimes just called corticotropin. Too much or too little can cause problems. The level of cortisol needs to be just right. Helping to balance the effect of insulin to keep the blood sugar level normal.(A hormone is a chemical which is made in one part of the body but passes into the bloodstream and has effects on other parts of the body.) You have two small adrenal glands which lie just above each kidney.Ĭortisol is vital for life. What is cortisol and what does it do?Ĭortisol is classed as a glucocorticoid hormone which is made by the adrenal glands. See the separate leaflet called Oral Steroids for a discussion on the possible problems associated with taking steroid medication. The rest of this leaflet is about Cushing's syndrome due to the body making too much cortisol. Women are five times more commonly affected than men. Most cases are in people aged between 20 and 50. About 5 in 1 million people develop this type of Cushing's syndrome each year. Cushing's syndrome, caused by the body making too much cortisol, is rare.
This condition was first described by a Dr Cushing who first wrote about it in the early 20th century. Cushing's syndrome can develop when your body makes too much of a hormone called cortisol (a main glucocorticoid). This means glucocorticoids made by your body. Long-term steroid medication is the most common reason for Cushing's syndrome to develop. It is long-term treatment with a steroid medicine that can cause Cushing's syndrome. Steroid medicines are sometimes used to treat various conditions such as some types of arthritis and some cancers. Prednisolone is the most commonly prescribed steroid medicine. These medicines are commonly called steroid (corticosteroid) medicines. This means you take a glucocorticoid medicine regularly.