They are benign tumours of the pituitary gland that secretes increased amounts of Adrenocorticotrophic hormone causing excessive cortisol production.
Ectopic ACTH syndrome:
The benign or malignant tumours that occurs outside the pituitary gland can produce ACTH. This condition is also known as ectopic ACTH syndrome. The tumours which produce ACTH are thymomas, pancreatic islet cell tumours and medullary carcinoma of thyroid.
The adrenal tumours might cause cushing’s syndrome. These non cancerous tumours called adrenal adenomas releases excess cortisol into the blood. Adrenocortical carcinomas or adrenal cancers are the least common cause of cushing’s syndrome. Cancer cells might release in the excessive secreation of cortisol and adrenal androgens. Adrenocortical carcinomas often cause very high hormone levels and rapid onset of symptoms.
Familial Cushing’s syndrome:
Some individuals may develop cushing’s syndrome can occurs due to an inherited tendency to develop tumours of one or more endocrine glands. In primary pigmented micronodular adrenal disease, children or young adults develop small cortisol-producing tumors of the adrenal glands. In multiple endocrine neoplasia I (MEN I), hormone-secreting tumors.
Cushing syndrome can also occur for the patients who is taking the oral corticosteroids for prolonged period of time.