Cushing’s Disease
Cushing’s disease is caused by pituitary adenomas that secrete ACTH. The unregulated secretion of ACTH causes abnormally high levels of cortisol, a steroid hormone produced by the adrenal glands.
Widened purple striae in a patient with Cushing's syndrome.
The normal diurnal variation in salivary cortisol production excludes a diagnosis of Cushing's syndrome.
Marked adrenal enlargement in a patient with Cushing's syndrome due to ectopic ACTH hypersecretion.
Symptoms
Cushing’s disease can be very difficult to diagnose and often patients will have prolonged symptoms before a diagnosis is made. Hypercortisolemia affects almost every organ in the body. It causes hypertension, diabetes mellitus, osteoporosis, rounding of the face, truncal weight gain, abdominal striae (stretch marks), and development of an upper back fat pad ("buffalo hump"). Cortisol is a very potent hormone and even slight increases over time can result in symptoms. Neuroendocrinologists often use dexamethasone suppression tests to diagnose Cushing’s disease.
Treatment
Treatment of Cushing’s disease entails removal of the tumor by transsphenoidal surgery. Because these tumors are often very small and invasive, surgery should be performed by surgeons with significant experience with Cushing’s disease. For cases in which the tumor is not found, removal of half the pituitary gland (called a hemihypophysectomy) guided by inferior petrosal sinus sampling may lead to cure in a majority of patients. Those patients not rendered disease free by surgery are often treated with medications to lower cortisol. Radiotherapy is often administered to destroy the tumor. Total bilateral adrenalectomy is considered one of the last treatment options in patients with persistent or recurrent Cushing’s disease, who have not received benefit from other therapies. For these patients, the drastic cortisol deprivation can trigger a boost in the growth and ACTH-secretion of the tumor.
Left: Cushing's disease due to a right-sided ACTH-secreting microadenoma. Right: Cushing's disease due to a left-sided invasive ACTH-secreting macroadenoma.
Patients with long-standing elevated cortisol levels have isolated hypothalamic-pituitary suppression, and following successful treatment of the Cushing’s syndrome, patients will require replacement cortisol therapy for 6 to 12 months, or until CRH and ACTH production returns to normal.
Patient Guide to Residual Cushing's Disease (PDF)
Web site for the Cushing's Understanding Support & Help Organization
